All functionality which is not related to a ResourceTreeModel has been
moved into ResourceModel base class, allowing to share them in other
resource model implementations.
Added initial support for dragging ResourceItems. This is achieved by
using drag'n'drop support offered by Qt's model/view technology.
Signed-off-by: Tobias Doerffel <tobias.doerffel@gmail.com>
Naming classes like ResourcesItem or ResourcesDatabase is bad style,
therefore rename all classes and files to be Resource*.
Signed-off-by: Tobias Doerffel <tobias.doerffel@gmail.com>
