2.0 taxonomy tweaks

- Don't display other plugin's types in menu links
- When editing a vocabulary, only display relevant types

Use case: If we have 2 vocabularies:

	- Categories
		Announcements
		Uncategorized
	- Places (from plugin Places)
		Bars
		Restaurants

When editing 'Categories' vocabulary, we should not allow types belonging
to Places plugin to be selectable in the select box.