SERVER-13635 Replaces high-level references to Record  with RecordData class.

In order to allow the use of certain types of storage engines, it was
necessary to replace some use of the Record class. The Record class is
now almost entirely restricted to the mmapV1 level and below.
Higher-level uses of the Record class were replaced with calls to the
new RecordData class.
Merge branch 'master' of https://github.com/mongodb/mongo
Merge branch 'master' of https://github.com/mongodb/mongo
Merge branch 'master' of https://github.com/mongodb/mongo
deleted extra #include that was causing errors
fixed compile errors
wrote save and recover position methods in rocks_btree_impl.cpp, added snapshots for cursors, a little other cleanup stuff
pulled from upstream/master
Merge branch 'master' of https://github.com/mongodb/mongo
Merge branch 'master' of https://github.com/alexkleiman/mongo-1 into RocksDB
added tests for RocksBtreeImpl::savePosition() and RocksBtreeImpl::restorePosition()
updates record store, mostly done
merging
moved constant into a static variable
Merge branch 'RocksDB' of https://github.com/alexkleiman/mongo-1 into RocksDB
wrote tests to cover all of rocks record store, all pass
wrote RocksCollectionCatalogEntry::removeIndex()
Merge branch 'RocksDB' of https://github.com/alexkleiman/mongo-1 into RocksDB
fixed... yis
made a few comments