Add Mather app
Mather: Licensed GPLv3+. Straightforward build via gradle
. Versioned as semver via git tags.
I've tested the build (via fdroidserver) with SDK version 25.1.7, Build Tools version 24.0.1, Android Platform version 23, Android Support version 23.2.1.
Relevant Submission Queue thread: https://f-droid.org/forums/topic/mather/