SERVER-16520 ClientCursor keeps ptr to owning CollectionCursorCache

Changes ClientCursor::_collection to ClientCursor::_cursorCache, and
updates ClientCursor/ClientCursorPin interfaces accordingly.
SERVER-16520 Rename CollectionCursorCache to CursorManager
SERVER-16520 Add a global CursorManager

The global cursor manager owns ClientCursor objects that aren't
associated with a particular collection.

The auth check for getMore against cursors owned by the global cursor
manager is left as a TODO (tracked by SERVER-16657).
SERVER-16522 Update remaining jstests to use getCollectionInfos()
SERVER-16522 listCollections leave cursor open if >1 batch needed
SERVER-16523 listIndexes leave cursor open if >1 batch needed
BUMP 2.8.0-rc4
Merge remote-tracking branch 'upstream/master'