Savestate auto captioning

Description

This PR adds an auto captioning feature for savestates using RetroAchievements rich presence evaluation. To get the necessary data from the RetroAchievements API the user must login to their account from the game settings. This PR depends on this PR in game.libretro

Motivation and Context

I have opened an other PR for RetroPlayer that implements a savestate manager which displays the date-time that the savestate was created or a custom title, this PR gives savestates a title displaying what the player is currently doing in their game. This PR will stay as a draft until the savestate manager is merged and rebased to this version of kodi because there there are some changes that need to be done in order to work together.

How Has This Been Tested?

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)
[ ] Improvement (non-breaking change which improves existing functionality)
[X] 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
[ ] 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 / xbmc