Ampache API

* security
	* user can generate passwords to use with the Ampache API
	* ability to revoke those passwords
* new DB tables:
	* ampache_sessions - session tokens
	* ampache_users - generated passwords
* Ampache API (ADD and UPDATE parameters are unsupported yet):
	* handshake
	* ping
	* artists
	* artist_albums
	* album_songs
	* albums
	* artist_songs (also supports offset & limit)
	* songs
	* song
	* search_song
* delivery of music file with ampache token
* middleware to authenticate user with ampache token
Merge pull request #91 from owncloud/ampache

Ampache