Extend current implementation for various features

* splitted some db commands into multiple ones for easier maintenance
* counting images per album and write back the total number
* generating thumbnails for images

Signed-off-by: Simon Busch <morphis@gravedo.de>
Use luna-sysmgr-common to get platform grid unit value

Signed-off-by: Simon Busch <morphis@gravedo.de>
Remove verbose logging on thumbnail generation

Signed-off-by: Simon Busch <morphis@gravedo.de>