morebits: allow multiple elements in a subgroup

* Subgroup styling moved out to morebits.css
* Make subgroup IDs unique (except for 'option' elements; need to fix
this)
* Removing the attribute name="id" on every QuickForm
tag: add enhanced support for {{merge*}} tags

* Rationales can be posted on the article talk page.
* Multiple articles can be tagged at once with the appropriate merge
tag.