Close Directory / Store once all resources have been released

Currently we close the store and therefor the underlying directory
when the engine / shard is closed ie. during relocation etc. We also
just close it while there are still searches going on and/or we are
recovering from it. The recoveries might fail which is ok but searches
etc. will be working like pending fetch phases.

The contract of the Directory doesn't prevent to read from a stream
that was already opened before the Directory was closed but from a
system boundary perspective and from lifecycles that we test it seems
to be the right thing to do to wait until all resources are released.

Additionally it will also help to make sure everything is closed
properly before directories are closed itself.

The code needs some work though but I wanted to get it out there for discussion