Add View Variables plugin
Handle pre/post #261
Remove unneeded import of track.
Show variables for tracks without files
Show multi-value variables as lists.
Fix display of multi-value for id3v23
Add Album Artist Website plugin - see PICARD-26

Adds a plugin to get the artist homepage MB relationship and insert into
website (ID3 WOAR tag).

Note: I used this plugin as a trial for using a Picard xml module to
handle MB WS2 xml response. See PICARD-581.
Add NEWS.txt
Remove unneeded imports
Minor tweak to display if variable is null string
Handle album finalisation correctly.
Allow user to toggle debug mode from log dialog at runtime
Add new PICARD_BUILD_VERSION_STR

It can be set by external script at build time.
PICARD_VERSION should not be modified.

See http://tickets.musicbrainz.org/browse/PICARD-592
Merge pull request #289 from zas/build_version

Add new PICARD_BUILD_VERSION_STR
Add build scripts fro win and osx, add patch_version command to setup.py
Merge pull request #290 from zas/build_scripts

Add build scripts fro win and osx, add patch_version command to setup.py
Improve --version and About version display

Introduce PICARD_FANCY_VERSION_STR and simplify code.
Merge pull request #288 from zas/debug_mode

Allow user to toggle debug mode from log dialog at runtime
Update NEWS.txt
Prevent AttributeError when there is no "release_type_scores" option

It may happen during config option upgrade:
picard.config.ConfigUpgradeError: Error during config upgrade from version 1.3.0dev3 to 1.3.0dev4 using upgrade_to_v1_3_0_dev_4():
Traceback (most recent call last):
  File "./picard/config.py", line 141, in run_upgrade_hooks
    hook['func'](*hook['args'])
  File "./picard/config_upgrade.py", line 137, in upgrade_to_v1_3_0_dev_4
    _s[opt] = load_release_type_scores(_s.raw_value(opt))
  File "./picard/config_upgrade.py", line 126, in load_release_type_scores
    values = setting.split()
AttributeError: 'NoneType' object has no attribute 'split'

Reported in http://tickets.musicbrainz.org/browse/PICARD-592