socketapi: if the filename is empty, it's actually /
SocketAPI: Cleanup, removed helper namespace, added as private methods.
SocketAPI: Cache database conections and statements
Sql: New implementation of ownSql class to go away from Qt's own Sql
Merge branch 'sqlite_capi' of github.com:owncloud/mirall into sqlite_capi

Conflicts:
	src/mirall/socketapi.cpp