Fix enums for QML camera types.

CameraExposure, CameraFlash and CameraFocus had signals and functions
using enum-type arguments declared in QDeclarativeCamera. This doesn't
work since an enum and a function using it both need to be declared in
the same class in order to work from QML.
The relevant enums have been duplicated (not moved, in order to
preserve QML source compatibility) from QDeclarativeCamera to
QDeclarativeCameraExposure, QDeclarativeCameraFlash and
QDeclarativeCameraFocus.

Change-Id: Ib307d7c6c9dbc59b1b82782913397160be38d4cd
Reviewed-by: Christian Stromme <christian.stromme@digia.com>