Example and some sub features were missing in slcli image datacenter, slcli image edit

[ramkishor-ch]

1. slcli image datacenter
   a. Example was missing, please add it.
   EXAMPLE:
   sl image datacenter 12345678 --add dal05 --remove sjc03
   This command Add/Remove datacenter of an image.
   b. Options: --remove was not clearly unidentifiable, please add it.
   Options:
   --remove To remove Datacenter

Expected:

./slcli image datacenter --help
Usage: slcli image datacenter [OPTIONS] IDENTIFIER LOCATIONS...

EXAMPLE:
        slcli image datacenter 12345678 --add dal05 --remove sjc03
        This command Add/Remove datacenter of an image.

        Add/Remove datacenter of an image.

┌────┬────────────┬─────────────────────────────┐
│    │ identifier │                             │
│    │ --add      │ To add or remove Datacenter │
│    │ --remove │ To remove Datacenter │
│    │ locations  │                             │
│ -h │ --help     │ Show this message and exit. │
└────┴────────────┴─────────────────────────────┘

2. slcli image edit
   Example was missing, please add it.

EXAMPLE:
slcli image edit 12345678 --name ubuntu16 --note testing --tag staging
This command edits an image with ID 12345678 and set its name to "ubuntu16", note to "testing", and tag to "staging".

Expected:

./slcli image edit --help  
Usage: slcli image edit [OPTIONS] IDENTIFIER

EXAMPLE: 
   slcli image edit 12345678 --name ubuntu16 --note testing --tag staging
   This command edits an image with ID 12345678 and set its name to "ubuntu16", note to "testing", and tag to "staging".

        Edit details of an image.

┌────┬────────────┬───────────────────────────────┐
│    │ identifier │                               │
│    │ --name     │ Name of the image             │
│    │ --note     │ Additional note for the image │
│    │ --tag      │ Tags for the image            │
│ -h │ --help     │ Show this message and exit.   │
└────┴────────────┴───────────────────────────────┘

3. slcli image list
   Options: --private was missing, please add it.
   Options:
   --private Display only private images

Expected:

./slcli image list --help  
Usage: slcli image list [OPTIONS]

        List images.

┌────┬──────────┬─────────────────────────────────────────────────────────┐
│    │ --name   │ Filter on image name                                    │
│    │ --public │ Display only public images                   │
│    │ --private │ Display only private images                   │
│ -l │ --limit  │ How many results to get in one api call  [default: 100] │
│ -h │ --help   │ Show this message and exit.                             │
└────┴──────────┴─────────────────────────────────────────────────────────┘