Get Andoid build working again

Got PortaBase building for Android again, this time with Qt 5.15.0.

Wrote instructions so I won't need to re-discover them again
Switched Metakit compilation from android-autotools (which doesn't yet work with recent versions of the Android NDK) to a custom script following the NDK documentation: https://developer.android.com/ndk/guides/other_build_systems
Bumped some versions in androidManifest.xml
Removed some files auto-generated by Qt Creator so they won't end up with stale versions again
Updated portabase.pro for the switch from g++ to clang
Fixed an Android-specific bug in default alternating row colors

jmbowman / portabase