Add PLUGIN_CLASS_NAME declarations to plug-in projects

This is required for automatic static linking and deployment.
The test plug-ins are excluded from the automation based on
the assumption that they are usually not needed.

Change-Id: I7658c624101e3273767c1c10d77a87c89d5801ba
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>