Support .m4v files.

http://chatlogs.musicbrainz.org/musicbrainz/2013/2013-12/2013-12-08.html#T12-42-40-561267
Set QApplication.applicationName and organizationName

Those values are used by the QSettings class when it is constructed using the empty constructor.
This saves having to repeat this information each time a QSettings object is created.
Some libs (ie. Phonon) require those to be set
Emit a signal when selection is updated in the main window

Bump plugin api version to 1.3.0
Merge pull request #183 from zas/QCoreApplication

Set QApplication.applicationName and organizationName
Merge pull request #184 from zas/MainWindowSelectionUpdatedSignal

Emit a signal when selection is updated in the main window
USER_AGENT_STRING -> CLIENT_STRING, and use ORG/APP_NAME to build.
Append platform infos to user-agent string.

Exemple of output:
MusicBrainz-Picard/1.2.0final0 (Linux-3.5.0-17-generic-x86_64-with-LinuxMint-14-nadia;CPython-2.7.3)
Merge pull request #189 from Freso/support-m4v

Support .m4v files.
PICARD-539: ensure we append preferred encoding to normalized locale

http://tickets.musicbrainz.org/browse/PICARD-539
Update NEWS.txt
Merge pull request #190 from zas/useragent

Append system info to user-agent string, and build it from constants
Merge pull request #191 from zas/PICARD-539

PICARD-539: ensure we append preferred encoding to normalized locale