Added missing template for userarea and small tweak of CSS.
Changed plugget source registration: a form is now passed, instead of a default context.
Added decorator to check if a plugget is editable (avoid editing on front-end of some "system" pluggets).
Replaced "exclude" with "fields" due to the incoming deprecation of the first one.
Fixed validation of plugget title.
Cleaned up breadcrumbs-related templatetag library.
Fixed validation of bookmark title.
Changed default widget to textarea for "text" field of "TextPluggetForm".