Moved from using qtcontacts-tracker to qtcontacts-sqlite backend.
Because of this move, following features will not be available:
1) Custom details are not supported by sqlite backend. Because of this,
any google specific fields will not be supported. Also etag which was
being stored as a custom field cannot be stored. Because of this
updates/deletes to server will not be supported. Added a DEFINES to
remove support for custom details as of now
2) sqlite backend does not support EventAdded, EventModified and also
does not update QContactTimestamp incase of updates. Because of this
slow-sync cannot be supported
3) Support for avatars is missing
Tested 2-way slow sync and it works fine.

Signed-off-by: Sateesh Kavuri <sateesh@mobilitas.co>