changes to the mobile builds

[Dirk Hohndel]

I did some fairly significant changes to the way we build the iOS and Android mobile apps.
Those of you how are subscribed to our "closed" testing groups should have received notifications that updated apps (version 3.1.0) are available for testing.
I'll push this into the "open" Android testing as well.

What has changed? 

- we now build both iOS and Android apps from the same qmake configuration
- because of that, the way some resources are bundled has changed --> I'd love to hear if all of the localizations are still working as intended, especially on iOS
- we switched to some newer support libraries (I haven't switched iOS to Qt 5.15, yet - there just aren't enough hours in the day)
- the Android build is now an app bundle and no longer an apk, following the current practices requested by Google
- because of that pretty much everything about the Android build had to change. As mentioned, I switched it from cmake to qmake, I upgraded a lot of libraries, but also the way everything is assembled is fundamentally different

Please test these new binaries. Test simple things (can you update cloud storage - do you see the updates on your desktop). Test things we often forget to test (can you get to the user manual? can you edit dives? can you run the GPS service? can you tap on dive locations and get a map?)
And of course test downloading from various dive computers.

Especially on Android this is maybe the most significant set of changes that I've made in over a year. I'd really love to not have our end users find all of the bugs that this is causing.

Thanks for your help

/D