fixing the stats display

enable hide/unhide of vtol and survey stats

adding check for surveying item

setting distance units and check if vtol

add active vehicle

check for valid mission

requested changes

Android done.

Signed-off-by: Tomaz Canabrava <tomaz.canabrava@intel.com>

Signed-off-by: Tomaz Canabrava <tomaz.canabrava@intel.com>

- Load/Save working
- Entry point working

Plus new unit tests

Also additional major Mission usability changes

Add scroll height indicators to Flickable