Add several methods for DB Mappers and Entities

* DB Mapper & Entities:
	* Album added attributes: trackCount, artist (both not filled by default)
	* Album added methods: getNameString (returns an translated string for unknown artists)
	* AlbumMapper added methods: count, countByArtist, findAllByName
	* Artist added attributes: trackCount, albumCount (both not filled by default)
	* Artist added methods: getNameString (returns an translated string for unknown artists)
	* ArtistMapper added methods: count, findAllByName
	* Track added attributes: fileSize
	* TrackMapper: count methods now return actual count and not an array with 'COUNT(*)'
	* TrackMapper added methods: count, findAllByName, findAllByNameRecursive
	* add limit ScanStatus SQL
* Tests:
	* add L10nStub to properly mock the L10n class of ownCloud core
	* push test coverage to 100%
* Build:
	* add Makefile command to do PHP unit tests and create the test coverage
	* exclude external PHP files from test coverage
* Core API:
	* add call to register components to personal settings page
	* fix typos