Add new DropButton control - WIP

Icons for Map Display

[WIP] appveyor windows builds

No widgets in mobile builds

Fixed QtLocation Caching

Home position manager

Updated Google Maps API Version
Updated User Agent used for map tile requests

Also:
- Remove unused code

Use import QGroundControl 1.0 to get to it

Take MissionManager off separate thread

travis-ci android add gstreamer

Change arm/disarm mavlink message usage

Support load/save

Fix APM adjustMavlinkMessage

Also understand the concept of missions which cannot be edited

This was done to support both PX4 and APM flight stack with same code

Previous code was horribly wrong.

Paramedter Editor search support

Added APM Firmware Plugin

- Also added new adjustMavlinkMessage support

Too complicated supporting both modes as editor becomes more complex

Joystick fix