Quadrotor 3d demo from ICRA paper

This pull request brings in my work from the ICRA 2015 paper on UAV trajectories. If you have the mosek and iris pods installed, you should be able to run the `runMixedIntegerForestSimple` demo or the much more complicated `runMixedIntegerForest` and `runMixedIntegerOffice` demos. 

`checkDependency` now supports 'iris' and 'mosek' as arguments.

If you don't have those pods, you should be able to run `examples/Quadrotor/test/testMISOSTrajectory()`, which only requires gurobi. 

This pull request also brings in Russ's work on the differentially flat quadrotor model and Scott V's work on the simple office environment for the quad.