Some comment cleanup, and fix so when closing the main window, it also closes the item select window

Change of name for diydrones fork of QGroundControl to APM Planner 2.0, per Chris Anderson and Craig Elder

Addition of requestReset to LinkInterface, to allow MavLinkProtocol to detect when connected, but at the wrong baud rate, request a reset.

Update README

Removed OpenGL dependency in HUD, merged in HUD from Soren Kuula and config changes from Michael Carpenter

This reverts commit 233a1716.

Impl. Lorenz suggestions wrt one velocityChanged, altitudeChanged, speedChanged signal per reference frame. Impl. CDI on compass disk.