Fix proguard optimization rules

Signed-off-by: Muntashir Al-Islam <muntashirakon@riseup.net>

Set up fastlane and fdroid variant

Signed-off-by: Muntashir Al-Islam <muntashirakon@riseup.net>

new preference for blind writing of control file

Added preferences for limit enforcing and immediate power event reaction

Added strong references to keep OnSharedPreferenceChangeListener inst…

…ances in memory, see end of https://developer.android.com/guide/topics/ui/settings.html#Listening