CONTENTBOX-75: Tagification of Widgets

Extensive updates/changes/additions/etc. to support inserting "tag"
based widgets in CKEditor. Also includes some extra definition data for
widgets (icon & category), as well as some UI changes to widget list
view and "insert" view for CKEditor.
CONTENTBOX-75: Reverted plugin names

Rolled back changes to plugin names where a space was added for display
purposes. This may break existing widget syntax, so should perhaps add
a new property if a custom display name is desired.
Merge pull request #65 from existdissolve/development

CONTENTBOX-75: Tagification of Widgets