Add usage guide (#65)

* Add usage guide

Include usage guide to give detailed information about CLI features
and how to use CLI.

docs/guide/usage.md

@@ -0,0 +1,185 @@
+# Using the odfe-cli
+
+This section introduces you to many of the common features and options available in the 
+ODFE Command Line Interface (odfe-cli).
+
+
+**Topics**
++ [Getting help](./usage.md#getting-help)
++ [Command structure](./usage.md#command-structure)
++ [Specifying parameter values](./usage.md#specifying-parameter-values)
++ [Auto complete](./usage.md#auto-complete)
+
+
+## Getting help
+
+You can get help with any command when using the ODFE Command Line Interface.
+To do so, simply type `--help` or `help` at the end of a command name. 
+
+For example, the following command displays help for the general odfe-cli options and the available top-level commands. 
+
+```
+$ odfe-cli help
+
+odfe-cli is a unified command line interface for managing ODFE clusters
+
+Usage:
+  odfe-cli [command]
+
+Available Commands:
+  ad          Manage the Anomaly Detection plugin
+  completion  Generate completion script for your shell
+  curl        Manage Elasticsearch core features
+  help        Help about any command
+  knn         Manage the k-NN plugin
+  profile     Manage a collection of settings and credentials that you can apply to an odfe-cli command
+
+Flags:
+  -c, --config string    Configuration file for odfe-cli, default is /Users//.odfe-cli/config.yaml
+  -h, --help             Help for odfe-cli
+  -p, --profile string   Use a specific profile from your configuration file
+  -v, --version          Version for odfe-cli
+
+Use "odfe-cli [command] --help" for more information about a command.
+
+```
+
+For example, the following command displays Anomaly Detection plugin specific commands. 
+
+```
+$ odfe-cli ad help
+
+Use the Anomaly Detection commands to create, configure, and manage detectors.
+
+Usage:
+  odfe-cli ad [command]
+
+Available Commands:
+  create      Create detectors based on JSON files
+  delete      Delete detectors based on a list of IDs, names, or name regex patterns
+  get         Get detectors based on a list of IDs, names, or name regex patterns
+  start       Start detectors based on a list of IDs, names, or name regex patterns
+  stop        Stop detectors based on a list of IDs, names, or name regex patterns
+  update      Update detectors based on JSON files
+
+Flags:
+  -h, --help   Help for Anomaly Detection
+
+Global Flags:
+  -c, --config string    Configuration file for odfe-cli, default is /Users/opendistro/.odfe-cli/config.yaml
+  -p, --profile string   Use a specific profile from your configuration file
+
+Use "odfe-cli ad [command] --help" for more information about a command.
+
+```
+
+
+## Command structure
+
+The odfe-cli uses a multipart structure on the command line that must be specified in this order:
+
+1. The base call to the `odfe-cli` program.
+
+1. The top-level command, which typically corresponds to OpenDistro plugins supported by the odfe-cli.
+
+1. The subcommand that specifies which operation to perform.
+
+1. General CLI flags or parameters required by the operation.
+
+    ```
+    $ odfe-cli <command> <subcommand> [flags and parameters]
+    ```
+
+## Specifying parameter values
+
+Many flags used in the odfe-cli are simple string, numeric values or boolean, such as the path and pretty in the following example. 
+Here, path accepts string value while pretty is a boolean flag.
+
+**Note:** you must use quotation marks around strings that include one or more space characters
+```
+$ odfe-cli curl get --path _cluster/health --pretty
+```
+
+## Auto complete
+odfe-cli includes a command-completion feature that enables you to use the Tab key to complete a partially entered command.
+This feature isn't automatically installed, you need to configure it manually.
+
+### Configure auto complete
+
+To enable the auto complete feature, you can use the following command and perform operation as mentioned in the help,
+based on your operating system
+```
+odfe-cli completion --help
+
+To enable shell autocompletion:
+
+Bash:
+
+$ source <(odfe-cli completion bash)
+
+# To enable auto completion for commands for each session, execute once:
+Linux:
+  $ odfe-cli completion bash > /etc/bash_completion.d/odfe-cli
+MacOS:
+  $ odfe-cli completion bash > /usr/local/etc/bash_completion.d/odfe-cli
+
+Zsh:
+
+# If shell completion is not already enabled in your environment you will need
+# to enable it.  You can execute the following once:
+
+$ echo "autoload -U compinit; compinit" >> ~/.zshrc
+
+# To enable auto completion for commands for each session, execute once:
+$ odfe-cli completion zsh > "${fpath[1]}/_odfe-cli"
+
+# You will need to start a new shell for this setup to take effect.
+
+Fish:
+
+$ odfe-cli completion fish | source
+
+# To enable auto completion for commands for each session, execute once:
+$ odfe-cli completion fish > ~/.config/fish/completions/odfe-cli.fish
+
+Powershell:
+
+PS> odfe-cli completion powershell | Out-String | Invoke-Expression
+
+# To enable auto completion for commands for each session, execute once:
+PS> odfe-cli completion powershell > odfe-cli.ps1
+# and source this file from your powershell profile.
+
+Usage:
+  odfe-cli completion [ bash | zsh | fish | powershell ]
+
+Flags:
+  -h, --help   help for completion
+
+Global Flags:
+  -c, --config string    Configuration file for odfe-cli, default is /Users/opendistro/.odfe-cli/config.yaml
+  -p, --profile string   Use a specific profile from your configuration file
+
+```
+### How to use Auto complete
+When you partially enter a command, parameter, or flag, the command-completion feature either automatically
+completes your command or displays a suggested list of commands. To prompt command completion, you partially enter a command and press Tab.
+
+The following examples show different ways that you can use command completion:
+* Partially enter a command and press Tab to display a suggested list of commands.                                                                                      
+```
+odfe-cli curl p[tab key]
+post    put 
+```
+* Partially enter a parameter and press Tab to display a suggested list of parameters.
+
+```
+odfe-cli curl get --[tab key]
+--config          --data            --filter-path     --headers         --help            --output-format=  --path=           --profile         --query-params    
+--config=         --data=           --filter-path=    --headers=        --output-format   --path            --pretty          --profile=        --query-params= 
+```
+* Enter a command and press Tab to display sub commands.
+```
+odfe-cli curl [tab key]
+delete  get     post    put     
+```