Use show_admin_column for taxonomies.

Introduced in 3.5, the show_admin_column option cuts down on the amount
of extra code we would otherwise need to render these columns in the
administrative interface.
Don't change column names for AJAX calls.
Add collection ID label to collection settings pages.

It's extremely useful for users to know the actual collection ID–like
webcomic42–when using various template tags, so adding it in a
prominent but not distracting place should be helpful.
Include webcomics on all archive pages.

This ensures webcomic's show up in category, tag, date, and other types
of WordPress archive pages. Fixes #92
Add slug collection setting.

This always existed behind the scenes, but it'll be useful for users to
be able to customize it once crossover characters and storylines are
fully implemented.
Clean up configuration pages.

Make the collection settings pages more consistent with other WordPress
pages and remove "Settings" from each of the section titles.
Update help information for new Slug setting.
Correct $gestures checkin dynamic widget.
Enhance custom template handling.

Use template_include instead of template_redirect. Now automatically
handles overriding normal template files with Webcomic-specific
templates for Webcomic-related pages by placing appropriate templates
inside of a 'webcomic' folder in the current theme.
Set post title to empty string when titles are disabled.
Add crossover term support.

Includes several new template tags and shortcodes, a new ep_mask for
taxonomy archives, and various fixes to template handling. Closes #83