Rc param tune

A first test version of the UI for configuring the RC to Parameter mapping: The process is initiated by the user by opening the new context menu in the parameter view. The dialog window then makes sure that the param value which the user sees is up to date and lets the user configure the options before sending the mapping via mavlink.

![screenshot from 2014-12-28 23 46 52](https://cloud.githubusercontent.com/assets/1419479/5565209/ecef967c-8eeb-11e4-9775-d8f0894744fd.png)

![screenshot from 2014-12-28 23 35 15](https://cloud.githubusercontent.com/assets/1419479/5565198/e3572572-8eea-11e4-89c6-6785cb8b890d.png)

More docs will follow.

mavlink PR: https://github.com/mavlink/mavlink/pull/309
px4 PR: https://github.com/PX4/Firmware/pull/1543

This will fail teamcity because of the mavlink update.  As soon as the mavlink PR is in I will update the submodule here.
This needs to be copied to a char[16] and then the char[16] passed to _pack. Otherwise it can cause a crash when the mavlink code does a memcpy on the full 16 bytes.