Check referential integrity when deleting node
Refactored local indexing
Working on deindexing

TODO:

- Traverse the nodes subtree when deleting (not just a filesystem
  recursive delete)
- Remove indexes pertaining to delete nodes
- Create NodeDeleter class

- Create a wrapper for the Jackalope node structure (Model\Node)
- Have methods such as ->getUuid(), ->getIntrenalUuuid, getReferences
  etc.