Adaptions for FDroid build / Translation updates

FDroid build support

• changed FDroid metadata to use gradle build system
• change method of library inclusion to allow FDroid build jar from sources
• change git inclusion of plugin library from submodule to subtree to allow easy FDroid updates w/o parameter changes.

Translation updates

• Update Portugese (Brazil) ( Thanks to @AurelianoBR )
• Update Belarusian ( Thanks to @victorenator )