[Reduce Manual Work] Modify help message to conform to CLI convention

[fengzhou-msft]

Issue:
Some of the generated help messages from swagger do not conform to CLI convention and need to be modified manually.

1. Verbs should use original form instead of third person singular form.
2. Example names should use a sentence instead of snake case words. For instance: Factories_Delete should be Delete a factory.
3. The help message for create command and update command should be different instead of the same create or update ....(This is already fixed in latest version)
4. Help message for the root level command group is missing.

Impact:
Reduce the work amount of copying a lot of help messages under manual folder and then modify them manually.