Port to SDL2
Removed SDL from test target
Seperated Joystick Error and solved Race

        - Race condition on joystick thread destruction solved
        - Switch back to SDL1 because of Event Bug
Solved Race in Comm Thread destruction
Enhanced closing of program

        - Program now closed correctly with CTRL-C and Window closing
Merge branch 'gui' of https://github.com/steup/mobilePI into gui

Conflicts:
	include/JoystickError.h
	src/Joystick.cpp