Added UniqueAttribute column constraint.
Added UniqueAttribute column constraint.

praeclarum/sqlite-net,igrali/SQLite.Net-PCL,Y-Less/sqlite-net,daynin/net-sqlite,nicolehaugen79/sqlite-net,jorik041/sqlite-net,CutFlame/sqlite-net,fernandovm/SQLite.Net-PCL,haithemaraissia/sqlite-net,daynin/net-sqlite,arlm/sqlite-net,pedropaf/sqlite-net,mattleibow/SQLite.Net-PCL,caseydedore/SQLite.Net-PCL,oysteinkrog/SQLite.Net-PCL,peterhuene/sqlite-net,ericsink/sqlite-net,koush/sqlite-net,JAgostoni/sqlite-net,molinch/SQLite.Net-PCL,peterhuene/sqlite-net,CutFlame/sqlite-net,igrali/SQLite.Net-PCL,Applied-Duality/sqlite-net,TiendaNube/SQLite.Net-PCL,kreuzhofer/SQLite.Net-PCL,koush/sqlite-net