Sub features and Example were missing in slcli cdn edit, slcli cdn origin-add

[ramkishor-ch]

Hi @allmightyspiff,

Fixes: #2019

Title:
Added Sub features and Example in slcli cdn edit, slcli cdn origin-add

Description:

1. I have added sub feature cache-description in ./slcli cdn edit --help
2. I have added Example and sub features like https port, compression, dynamic-path, prefetching in ./slcli cdn origin-add --help.

Please review it.

Please find the screen shots.

Screen Shot: 1

Screen Shot: 2

Screen Shot: 3

Screen Shot: 4

Screen Shot: 5

Thanks,
Ramkishor Chaladi.