Revert "Removed custom_slug and cache_pages_backend."

This reverts commit 161e30143aace8a8d3cc6babbbd96f0b57c8d4be.

Conflicts:
	pages/app/models/refinery/page.rb
Revert "Use menu_title_or_title method where appropriate."

This reverts commit 55bd704f415ee7027b797ce6dbf79d695905e869.
Don't cache admin pages records.
Merge pull request #2498 from zizkovrb/make-Xanders-happy-again

Revert "Removed custom_slug and cache_pages_backend."