UI Tweaks for all mobile platforms.

all calls to qsTr are done, if I didn't forget anything,
on the PX4 QML files.
Signed-off-by: Tomaz Canabrava <tomaz.canabrava@intel.com>

Add scroll height indicators to Flickable

- New MissionManager
- Plumb MissionManager through MissionEditor
- Mission Editor supports get/set

Airframe QML: Fix order-dependency of config. Highlight selected airframe more clearly. Allow combo box action to select the airframe as well. Allow single click on icon to select airframe.

Using wrong control

- More more on making QGCView real
- Converted Parameter Editor to QGCView