Speeds things up especially when you have lots of matched fields that
share the same indexed field.

This code lies more then memory index but it is faster and doesn't lie
enough to break the FVH.

Also add term filtering to the analysis which saves a ton of time.

Nothing fancy for skipping the offsets for short documents like with the
FVH.

I have no idea if this is faster yet, but it ought to be less gnarly from
a memory standpoint.

This helps a bunch with memory but isn't perfect.

A few things we could really improve but I don't really feel like it now:
1.  Rebuild SliceWriter and SliceReader against Elasticsearch's IntArray
so that we can build a smaller and throw out XIntBlockPool.
2.  Cache the BytesRefHash between analyses - maybe use it instead of a
Set<String> for filtering and use the term that spits out the BytesRef
and the hashcode of the field at the same time.

It wasn't helping

We'll add this back in another pull request.