[GSoC 2020] Python Game API

[NikosSiak]

Description

This PR extends the Python API to support game metadata, like title, developer, publisher and captions (from #120 ).

Motivation and Context

How Has This Been Tested?

I have wrote a small addon that uses the API to update the discord rich presence status displaying what game you are playing and what you are doing in the game at this moment https://github.com/NikosSiak/service.games.discord.richpresence

Screenshots (if appropriate):

Types of change

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] Clean up (non-breaking change which removes non-working, unmaintained functionality)
• [x] Improvement (non-breaking change which improves existing functionality)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that will cause existing functionality to change)
• [ ] Cosmetic change (non-breaking change that doesn't touch code)
• [ ] None of the above (please explain below)

Checklist:

• [x] My code follows the Code Guidelines of this project
• [x] My change requires a change to the documentation, either Doxygen or wiki
• [x] I have updated the documentation accordingly
• [x] I have read the Contributing document
• [ ] I have added tests to cover my change
• [ ] All new and existing tests passed

[garbear]

I've created a test build and uploaded to https://github.com/garbear/xbmc/releases. I tested it out and everything looks good for me. Only issue was the login button in the settings taking a while to give user feedback during the network IO. Adding a spinner would be a good idea.

My only two comments left about the code are the unused variable and the copyright headers.