Rework mission lines + various mission-related bug fixes

Fixes ardupilot abbreviations for #3588

Remove animation to save perf

Bump joystick settle constant

Instantiating QSettings on the stack is quite expensive (full file read+parse each time) and this was done in a tight loop with mission items as they were dragged. Very slow.

PX4 mode cleanup

MockLink: Support multi-vehicle simulation

Move message area to top

Virtual joystick: Throttle no longer spring loaded to center

Mobile file dialog: Add logging

- Delay gps position for better testing
- Longer delay on home position

Height will shrink to fit small text heights

This allows you to arm

Settings real estate

Planned Home Position: Tweaks to wording to help with confusion

MapScale: Add support for feet/miles

Handle parameters at end of URL

Offline Map: Add preview and zoom numbers