Reorganized code again, added smux module (see notes)

I rearranged a little bit how the #defines are handled, that way a user
can include just a specific submodule and not have to worry about
including the corresponding hitechnic libraries. I also added an smux
module that is basically the same thing as the normal one but has
support for the smux, as well as a quick (yet untested) preprocessor
#define to make setting up smux sensors easier. It does not seem to
compile but I'm certain that it's valid as RobotC is just complaining
about 'tSensors' over 'tMUXSensor.' I'll see if it works after a
restart, sometimes this happens to me.