Make dispatch bundle friendly, all changes required in mapper.

Summary:
Abstracted a little and stopped forcing a resolve path in normalize
Allow dispatch to look for bundls currently it only looks into the vendor directory
Document a little

Test Plan: include some resources from bundles, make sure mapped and non mapped turn up as well as with and without entity map. Also make sure nothing else breaks

Reviewers: brooke

Reviewed By: brooke

Maniphest Tasks: T40

Differential Revision: http://phabricator.cubex.io/D6