Allow for nicer JSON input in API

##### ISSUE TYPE
- Feature Idea

##### COMPONENT NAME
- API

##### SUMMARY

There are many places where the API takes a string input that is a JSON field. (Sat6 group patterns, extra_vars, etc)

Passing this data generally involves a lot of quoting. It may be useful to have a cleaner way to input this data.

##### ENVIRONMENT
* AWX version: current

##### ADDITIONAL INFORMATION

Start by reviewing the API entry points for fields such as Sat6 group patterns and extra_vars, and trace how their string inputs are parsed. Define the expected cleaner input form and verify that these fields can accept it without extensive quoting.

Written by the indexing model from the issue text.