updated section model and content_type model to handle dynamic user content blocks
Merge branch 'content_block_path_menu_bug' of github.com:jtwohiou/browsercms into jtwohiou-content_block_path_menu_bug
[#602] Addressable content can be landing pages.

* Slight change to logic so that any addressable content types can serve as landing pages.
* This allows 'core' content types like Forms which are addressable to serve, as well as exclude external content types that aren't addressable.