Use a smarter method to extract track number from filename.

When file has no metadata field indicating the track number, Picard
is trying to guess it from filename, but the simple regex wasn't very efficient.

tracknum_from_filename() does a much better job.
A test case was added.
Add options to control browser integration (enabled/disabled and listening port)
Rename "Web Proxy" option page to "Network"

Settings for web proxy are still there, but we'll add browser integration
options to this option page too.
Move Browser Integration options to Advanced > Network option page
Add a real life test for track number case extraction
Remove now unused FileLookup._encode().
Merge pull request #154 from zas/browser_options

Browser options
Move constant regexps outside the `tracknum_from_filename()` function
Merge pull request #151 from zas/tracknum

Use a smarter method to extract track number from filename.
Add config "color" section to store colors
Rename config.setting.color_* to config.color.item_*

* Add a hook in tagger.py to handle this change
* Read config.setting.color_* values, store to config.color.item_*
* Delete old options
* bump picard version to 1.3.0dev1 to force config upgrade

It serves as a test case for the recently added config upgrade handling code.
Make tag status colors configurable (not yet through UI).
Add an optional description to options.
Add simple descriptions to tag_*_fg color options
Add generators to get list of options in a section

```python
# print keys for all options in config
for key in config.Option.keys():
   print key  # key = "section/name"

# print descriptions of all options in the color section
for i in config.color.keys():
   print config.color.get_description(i)
```
Add description to itemviews colors
ConfigSection: add method to retreive default value
Add option panel for configuring colors

For now, color changes may not be shown immediatly, it requires to alter code
because it was made for "constant" colors.
logview: make log colors configurable
Add "Changes here may not take effect until Picard is restarted." disclaimer.