Initialize sensors, set up FlightComputer singleton structure

[cschow-ucsd]

• Providers to provide singleton input/output devices
• Remove getInstance() methods in most classes, in favor of initializing all objects in FlightComputer
• Builder pattern to construct customized FlightComputer instances

Partially addresses #52, but returning different sensors/simulators has not been completed in SensorProvider.

[Pumuckl007]

Could you change the tab size to 2 spaces, not four. Other than that it looks really good and I think it should work well.

[Pumuckl007]

If you are going to reformat all of the code can you make sure to keep the alignment the same. The variable declarations should stack the equals signs. Like this:

[cschow-ucsd]

Field declarations should be aligned now.
Previously only local variables and assignments were aligned.