Official SMASH Version 1.9.1 for F-Droid

Release notes:

This is mainly a bugfix release, also made to enhance two way synch with the server.

Apart of that there are some minor changes:

• possibility to select a theme for mapsforge offline maps
• better UI

• layers visibility has now a proper icon
• the gps info box is not a bottom sheet

A big thanks for this release goes to @sanak , that helped to fix the dependencies and upgrade madness that came with the new flutter upgrade.