Quadrotor

Changed max thrust in nav_lib and set thrust to 0 in mk_wrapper

Tested joystick_control with the quadrotor, and it works! And it now has
enough thrust to get it off the ground.

Major changes in mikrokopter for lost connection

-In nav_lib.cpp, added main_loop, so we don't have to keep rewriting it
:). Also, this now publishes to /mk_wrapper/control, which should be
used from now on. However, old publish_on still works as it did....