Fix null _activeVehicle references

Mission item fixes

Radio Cal: Only set reverse for multi-rotor

Fix references to __qgcPal which did not exist in control

Only accept numbers in FactTextEdit

Found a unused class, safe to remove.

All facts are numeric, atm. this means that the input should only
accept numbers. it already had the     inputMethodHints:   Qt.ImhFormattedNumbersOnly
option, but for some reason it still accepted letters and symbols.
by adding a     validator: DoubleValidator {} we limit the characters
to numbers only - and if the value is a integer, it will still work.

Tested by adding waypoints on the map & messing with the GPS coordinates.
Signed-off-by: Tomaz Canabrava <tomaz.canabrava@intel.com>

Update for new Clang errors

Fix layout of mission item status values

Fix Message Indicator display

Much better Outdoor palette visuals

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

Toolbar/Instruments respect palette

Fix for espeak / alsa errors for #3015

Map control use different border color based on map type

Initialize espeak in async playback mode and explicitly synchronize after each synth operation in the worker thread.

Improve travis.yml readability

Also fix problem with log files over 4M causing build failure

Don't use channel 0 to avoid sequence number problems

APM PreArm message handling

adding follow me

Travis: Use Qt5.5 download for OSX