Fix lost 2i AAE tree on rebuild
Clean up 2i knowledge in vnode hashtree

Now only one place creates the list of index/n's based on the vnode
hashtree state. A new flag is passed in as a startup option indicating
whether 2i data will be indexed.
Merge pull request #780 from basho/bugfix/2i-aae-tree-rebuild

Fix lost 2i AAE tree on rebuild