Show correct item editor based on current VTOL state

LinkInterface and Vehicle uses mutexes to synchronize writing bytes to the link instead of queued signals

App messages now use simple modal message dialogs. Vehicle messages continue to use non-modal popup.

Also fixed bug with ArduPilot guided waypoint write which would trash
existing mission.

* Resume index adjust to previous coordinate command
* Takeoff always added to resume mission
* Remove camera id checks which are no longer part of spec
* Simplified de-dup logic

Remove/comment off debug output pollution

This time to handle correctly updating plan/fly view when plan changes

Works around ArduPilot strangeness with empty missions end

Must memset structures before use.

Fixed a pile of bugs as well

Plus low battery announce changes