Indentation and spacing fixes, according to PEP8
Merge pull request #193 from zas/pep8

Indentation and spacing fixes, according to PEP8, only cosmetic changes.
Ignore hidden files and directories based on `show_hidden_files` option.

http://tickets.musicbrainz.org/browse/PICARD-528
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.