Feature Request: User defined buttons

It would be a great feature to have a number of buttons on one of the tabs that the user could configure.
I imagine it would be like missions, but wouldn't need to have way points and such.
The commands would be mavlink based commands.
I guess this already possible by selecting a pre-made script, but then the pilot still has to send the script to the craft and invoke auto-mode. The buttons would do it all automatically.

The issue names no files, tests, or entry points. Start by locating the Mission Planner tab and existing mission or script-invocation UI, then clarify the button configuration and MAVLink command flow; done means configurable buttons can send the selected commands and handle the described setup automatically.

Written by the indexing model from the issue text.