MythMusic: hunt for tracks in the 'Music' storage group

This is just for testing and currently only looks on the master backend and
only if it wasn't found in the local music directory.
MythMusic: allow seeking when playing back from a storage group
MythMusic: re-factor the IODevice handling

This makes the various DecoderIOFactory*'s responsible for the IODevice they
create and avoids passing pointers to them around.
fix typo
New Netherlands locale file
from tycholursen@gmail.com

Thank you!

closes #11502

Signed-off-by: Nicolas Riendeau <nriendeau@mythtv.org>
update mythtranscode to work with ac3 with newer ffmpeg

ffmpeg has moved the duration/size of the audio frame to another place, so look
there

links used to figure it out how to move forward
http://ffmpeg.org/trac/ffmpeg/ticket/1240
http://git.videolan.org/?p=ffmpeg.git;a=commitdiff;h=364c71c80e9124a2624e3bfeb8e84c5cddeda222
http://code.mythtv.org/trac/ticket/2077#comment:42

thanks to Nicolas Pöhlmann for finding the commit that broke it

Refs: #2077
Update the doxygen config using doxygen -u
Enable DOT for Doxygen graphs
add NULL check missed in [a9b90652]

found by Jim Stichnoth

Refs #2077
split position and duration map in mythtranscode

after [49dbed5b] a lossless transcode would run into untested code and
fail to insert the new position map

factor 1000 adjustment by Jim Stichnoth

Refs #10104
silence signedness warnings after upstream fix

the type of AV_NOPTS_VALUE has been fixed in
http://git.videolan.org/?p=ffmpeg.git;a=commitdiff;h=cb3591e69738c808d26ba15eb02414fedfcd91cc

note to self: suggest to use INT64_MIN upstream
Fix crash.

When playback request failed for whatever reason, if we were to check for the playback status it would crash due to ic being NULL.
Fix crash.

Fixes #11504
Properly handle multi-part http request in AirPlay video

This commit also adds the basics required to support AirPlay photo. Incidentally, properly handling multi-part data now allows to play videos from the iPhone "Photos" app.
Make the idle timeout independent of scheduler runs

As the scheduler runs every other minute when the EIT scanner is
enabled you end up with never being idle, thus breaking shutdown
when idle.

As discussed on IRC at
http://irc.mythtv.org/ircLog/channel/4/2013-03-14:18:52:00

Refs: #11399
MythMusic: look for coverart in the Music/MusicArt storage groups

If the track is in a storage group and the coverart is in the same directory
as the track then grab the coverart from there.

Embedded coverart will be cached in the MusicArt storage group and loaded from
there but the BE side of things is not yet implemented.
Merge branch 'master' of code.mythtv.org:mythtv
MythMusic: add storage group support in the AlbumArt visualiser
MythMusic: look for icons in the MusicArt storage group
MythMusic: move metadata and tag reading/writing to libmythmetadata

This allows both MythMusic and mythbackend/mythutils etc to use the same code.

NOTE: a distclean and re-run of configure in both core and plugins is required.
Also this makes TagLib a mandatory dependency of core MythTV.