Don't display other plugin's types in menu links
Initialize default variables to avoid undefined errors
When editing a vocabulary, only display relevant types

Use case:

Types:
	Nodes Plugin: Blog, Page, Node
	Places Plugin: Place

Vocabularies:
	- Categories (applicable to Blog, Page, and Node)
		Announcements
		Uncategorized
	- Places (applicable to Place)
		Bars
		Restaurants

When editing 'Categories' vocabulary, we should not list `Place`
Display type and vocabulary plugin info in admin_index
BCBREAK: Assume that `plugin` is null instead of null or ''

When 'plugin' is set, those records will only be available to the same
Types having the same 'plugin' value.

If it's null, then will be useable by all.
Update description if Term has the same id

This is a potential problem as a Term must have the same description
in all Vocabularies.  For example, an Announcement term might have
different descriptions between "Categories" vs "Product" vocabularies.
Merge branch '2.0-taxonomy-tweaks' into 2.0