Support the Jaikoz 'artists' tag, with help from @night199uk and @zas
Merge branch 'master' of github.com:musicbrainz/picard into artists-tag
Merge branch 'master' of github.com:musicbrainz/picard into artists-tag
Ignore hidden files and directories based on `show_hidden_files` option.

http://tickets.musicbrainz.org/browse/PICARD-528
Add "Ignore files according to show_hidden_files" to NEWS.txt
Move STYLESHEET_ERROR to parent class as it may be used in any page
Add ignore_regex option to Advanced options

Filepaths matching this regex will be ignored.
Add "ignore_regex ..." to NEWS.txt
Merge branch 'master' of github.com:musicbrainz/picard into artists-tag
PICARD-544: include socket module in exe

This is needed by urllib, which is imported since
26f20228eb95d4b55968e56796228bca7ebcffa7.
Merge pull request #199 from JonnyJD/exe_urllib

PICARD-544: include socket module in exe
Drop urllib dependency, use QUrl.toPercentEncoding instead of urllib.quote
Exclude socket module again, since it was only needed by urllib
Merge pull request #200 from zas/percentenc

Drop urllib dependency.
According to @JonnyJD, it saves around 250kb in win .exe.
transifex.net is deprecated, use transifex.com instead

http://support.transifex.com/customer/portal/questions/1160404-improve-ssl-security-for-transifex-net
tx client is giving a message about it too

Also add translation type 'PO'.
Merge pull request #201 from zas/transifex_update

transifex.net is deprecated, use transifex.com instead
Name upgrade functions after full version
Ensure each upgrade function is run only once
Move variable near where it is used
Define _s once in parent function