SERVER-9986 refactor near search for 2D and S2

Adds progressive search functionality for $geoNear operations,
allowing better integration with other cursors.
SERVER-14436 Fix signed-unsigned comparison compile error in unit test.
SERVER-14420 Get rid of global replSettings object
SERVER-14476 fixed LogRecordingScope to ignore log messages from background threads
SERVER-13989 convert some callers to new quota API
SERVER-13951 Plumb OperationContext into DBDirectClients used for writing
SERVER-14395 Clean up StorageEngine initialization and shutdown

* Added StorageEngine::cleanShutdown() and commented that the destructor will
  never be called.

* MMapV1StorageEngine specific operations were pulled into its constructor
  and cleanShutdown implementation.

* StorageEngines are now constructed at a point where it is safe to spawn
  threads.
SERVER-14503 move replHasDatabases to heartbeat.* from instance.*
SERVER-12750 disallow exhaust query option through mongos
SERVER-6352 Add sh.removeTagRange

Adding the removeTagRange helper to match addTagRange with some informational warnings that do not stop the operation from happening.

Note: does not address the fact that no feedback is given to indicate work done, or lack of work done (must check config.tags manually for results).
      This is also the case for addTagRange.

Closes #709

Signed-off-by: Benety Goh <benety@mongodb.com>
SERVER-14502 remove unnecessary check for NULL canonical query