Much better conversion of Mission to KML for use as 3d validation

[DonLakeFlyer]

This is a terrain based survey over hilly terrain:

Which leads to this KML output viewed in Google Earth:

Remove the .txt extension from here Test.kml.txt if you want to try this example yourself.

Other changes:

• QGroundControlQmlGlobal.globalPalette singleton can be used for cases where enable/disable state doesn't affect color choice. This prevent having to crank up new QGCPalette objects in Qml in various cases.
• MissionCommandUIInfo has new isTakeoffCommand field which can be used to determine if a command is one of the takeoff commands.

Related to #8510