implemented psn crawling for ps3 game metadata (mostly for thumbnails)
implemented game thumbnails for game embeds
fixed usage of dbcontext
some other bugfixes
RPCS3 Compatibility Bot reimplemented in C# for .NET Core
Current status of this PR:
* tested and targeted for .NET Core 2.1
* all functionality is either on par or improved compared to the python version
* compatibility with current bot.db should be preserved in all upgrade scenarios
* some bot management commands were changed (now under !sudo bot)
* standard help generator for the new discord client is ... different;
compatibility with old format could be restored through custom formatter if needed
* everything has been split in more loosely tied components for easier extensibility and maintenance
* log parsing has been rewritten and should work ~2x as fast
