Added initial changes that get some controller hotswapping into the game...

.... It still crashes after the second disconnection though.

This is a good start though: plugging a controller in mid-game or pulling it (just once) works.  This is also my first attempt to do a pull-request from using Monogame-SDL2 as an actual git repo inside of our project rather than just downloading the source & pasting it into our filesystem... so it's sort of a test-pull ;)