Refactor CLI

[techknowlogick]

👋 Hey, I know this is kinda a big PR and I'm thankful for you taking the time to even consider it. First, I want to say I understand that if this doesn't align with the current goal of the project that it may be closed, and that's totally ok with me.

Currently the CLI uses flags for both commands and options, this refactor switches it out to a format that allows for bashcompletion built in, and can auto-generate manpages.

For legacy sake, previous style of working with CLI still exists.

If the previous style of using only flags for everything is preferable, then this PR can be changed to still use urfave/cli, but still be flag only and would still provide the benefits of the refactored code style.

Please let me know if you have any questions.

Example help output:

NAME:
   WriteFreely - A beautifully pared-down blogging platform

USAGE:
   writefreely [global options] command [command options] [arguments...]

VERSION:
   WriteFreely 0.11.2

COMMANDS:
   user        user management tools
   db          db management tools
   config      config management tools
   keys        key management tools
   serve, web  Run web application
   help, h     Shows a list of commands or help for one command

GLOBAL OPTIONS:
   -c FILE        Load configuration from FILE (default: "config.ini")
   --debug        Enables debug logging (default: false)
   --help, -h     show help (default: false)
   --version, -v  print the version (default: false)

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• I have signed the CLA

[thebaer]

Thanks for working on this! It'll still be a while before I can fully test / review, but wanted to mention that I am definitely interested in merging this.

[thebaer]

Thanks again for making these changes! Looking forward to getting this merged.

Overall everything seems great, functionally -- and I appreciate the effort to keep this backward-compatible! I mostly propose some naming changes, and noticed some examples that need updating. Otherwise, might need to run go fmt on some files. With those changes, this should be good to go!

[techknowlogick]

@thebaer thanks for feedback. I've just pushed requested changes :)

[thebaer]

Thanks for the quick fixes! Looks great 👍 merging now.