* Add kdevelop to gitignore
* Add test stubs
* Rename px4_add_gtest to px4_add_unit_gtest
* Add infrastructure to run functional tests
* Add example tests with parameters and uorb messages
* Fix memory issues in destructors in uORB manager and CDev
* Add a more real-world test of the collision prevention
But fix the two crucial problems:
- When to begin the ramp?
There's a calculation now for the velocity ramp initial value
such that the resulting thrust is zero at the beginning.
- When to end the ramp?
The ramp is applied to the upwards velocity constraint and it
just ramps from the initial value to the velocity constraint
which is applied during flight. Slower/going down is always possible.