make Environment::dump method const

Signed-off-by: Shaun Verch <shaun.verch@10gen.com>
SERVER-12409 db.coll.remove() shell helper requires a query predicate
SERVER-12635 RSM should return ScopedDBConnection to pool
SERVER-12583 DBClientRS shouldn't use hosts the RSM thinks are down.

Also commented and ordered checks from cheapest to most expensive in
DBClientRS::checkLastHost.
SERVER-11498 Speed up sorter_test
SERVER-12591 renameCollection now checks that source and target namespaces are valid for user writes
Merge remote-tracking branch 'upstream/master'