Allow more than one logbook with the same app

[maesteve]

I have two logbooks, one for ultralight and another for gyrocopter. Currently, it's necessary to have two databases or two installations.

Add the option to switch logbooks while maintaining, Settings and Licensing & Certifications

[vsimakhin]

I was thinking about it, it will require some (actually a lot :) rewrites of code. I still would like to implement it in some way, but it's not a 5 minutes change, this will a be a new major release v3