Rename album_art_name_s to linked_names_s

Give the struct a more generic name so it can be re-used in other places

Conflicts:
	minidlna.c
Add setting to change metadata file name

New config option 'metadata_names' which can be a list of /-separated
files that get checked for metadata before the fallback <filename>.nfo
is checked. By default this metadata file is 'movie.nfo'
Add option to add list of (comma-separated) entries to DB

Refactor code to be able to read values from lists in the nfo metadata.
This enables us to add multiple actors/genres to media and serve them as
a part of metadata for clients. The XML library (minixml) is not ideal and
traverses the xml file backwards... *sigh*
Add new metadata info (year, actors, director)

minidlna already has support for these items, yet they
are never read from the NFO file. Use year if it exists
(instead of timestamp) and add actors & director
Support for short&long-descriptions

Add support for sending 'tagline' and proper long description
in the UPNP reply. Needs DB upgrade as there is new column

Conflicts:
	metadata.c
	metadata.h
Send more-appropiate reply for director and album-art

If mime-type is video, send director as upnp:director as
this is more understood by clients.
Also always send albumArtURI as this is read by some clients to show
icon of media file
DB upgrade is not performed if DB_VERSION is updated