better handling for pages with index in their name

[thescientist13]

Related Issue

resolves #455

Will track in Trello for post 1.0 release some ways to refactor / clean up a lot of this repeated page look up logic, like we have in the markdown / HTML transforms, as well as in the graph lifecycle. Maybe some sort of shared utility so we can avoid duplications, or at the very least, maybe this is a case to merge markdown and HTML transforms?

Summary of Changes

1. Better checking for pages that may include index as part of the page name (non "destructive" approach)
2. Enabled tests to verify the same
3. Although will be deprecated, Plugins -> Index Hooks docs are now working again