Make file loading more resilient

See (PICARD-605)[http://tickets.musicbrainz.org/browse/PICARD-605]
Add %_multiartist% and fix default renaming.

See http://forums.musicbrainz.org/viewtopic.php?pid=25318
Remove debug print statement
Add NEWS.
Use getall rather than split by ; (bitmap)
Handle NAT tracks with feat. artists.

Add %_primaryartist% and %_primaryartistsort% and use
%_primaryartist% in default naming string.
Revert "Handle NAT tracks with feat. artists."

This reverts commit 0707add3353455473f5ff26a117c7843d42cd4d5.
Switch to using artist rather than artists[0].
Merge NEWS items for compilation and multiartist.
Tweak NEWS (per mineo comment)
Put default script into a constant.
Add non-NAT and NAT tests
Fix default script for NAT tracks
Double-clicking on images in info dialog open them in external viewer
Display configuration file or registry path in debug log
Support ASF video file formats (reverted from commit 7494155d0c22bfb0fb479ef3613ba11a2993ec6d)
Support .ogv video files
Merge pull request #338 from zas/cover_art_show

Double-clicking on images in info dialog open them in external viewer
Merge pull request #339 from zas/config_path_in_debug

Display configuration file or registry path in debug log
Fix up albumartist_website plugin debug message

Traceback (most recent call last):
  File "picard\webservice.pyo", line 285, in _process_reply
  File "C:\Program Files (x86)\MusicBrainz Picard\plugins\albumartist_website.py", line 95, in website_process
    log.debug("%s: %r: Artist Official Homepages = %s", PLUGIN_NAME, artistId, url)
NameError: global name 'url' is not defined