Use ProGuard to reduce the size of binary builds. Also, all the unreferenced classes should be checked for problems/optimizations.
Use ProGuard for shrinking
Cancelled for now because DAVdroid and especially its libraries rely heavily on reflection; removing "unused" methods will cause errors. Renaming/obfuscation is not needed, so there's no need for ProGuard at all. Optimization should happen by removing dependencies.
Temporal relations are not necessarily causal relations.