Add menu item to display pages from collections

[cjbrooks12]

There's a MenuItem for displaying a single page using itemId, collectionType, and collectionId, but no menu items for displaying multiple pages from collectionType, and collectionId. As Orchid is moving more toward using that as the main mechanism for grouping/selecting/displaying pages, there should be a menu item for this.

Proposal

• Create a new collectionPages menu item, with collectionType, and collectionId properties
  • Also accept a list of pairs of the same, so that multiple collections may be aggregated into a single menu item, if needed. This should be mutually-exclusive to the pair at the top-level
  • Allow this menu to list pages flat, in a hierarchy by URL path, or a hierarchy by actual page parents
  • The title should be able to be customer with an arbitrary formatted, similar to the sourcedocPages menu item
• Deprecate some of the existing menu items that more-or-less do the same thing but are less idiomatic (pages from OrchidPages, latestPosts from OrchidPosts, wiki from OrchidWiki, etc.)
• Improve the collections generated by these plugins to give more flexibility in finding related pages

[cjbrooks12]

This is now added and released in 0.21.0