Config command support

[wtrocki]

Verification

[wtrocki@graphapi app-services-cli (config)]$ rhoas config devPreview true
Developer Preview commands activated. Use help command to view them.
[wtrocki@graphapi app-services-cli (config)]$ rhoas config devPreview trueds
Error: invalid argument "trueds" for "rhoas config devPreview"
[wtrocki@graphapi app-services-cli (config)]$ rhoas config devPreview false 
Developer Preview commands deactivated.
[wtrocki@graphapi app-services-cli (config)]$ 

Approach

In 0b79620 I have used single command approach and 2 arguments - one which is config key second is value.
I think that is overly complex and convoluted.
Current approach uses separate command for each key.

Drawback is for that approach we getting documentation file generated and there is little bit of duplication in docs, but much simpler and easier to work with.

What is outstanding

• base implementation
• unit tests
• Error handling mapping instead of system error
• I18n :)

[wtrocki]

@craicoverflow that will be quick review (small command/refactoring here)

[craicoverflow]

I suggest changing the command to dev-preview - all good otherwise