Reduce ramBufferSize, remove maxBufferDocs

* Reduce ramBufferSize to be on safe side for now and allow more
  memory to be available for caches.

* Remove maxBufferDocs completely to prevent additional flushing under
  constant indexing load.

Between the ramBufferSize and hard autoCommit settings I believe the
behavior is that 30 seconds or 32MB worth of documents could be lost
on process crash.  In the event this should happen AAE should trigger
repairs.