SERVER-15230 explain find via the find command
SERVER-14412 Fix the read lock assertion logic
SERVER-14668 fix locking issue in LockerImpl::dump
SERVER-15286 don't try to explode for sort if zero fields to explode
SERVER-15187 Update saved OperationContext in all PlanStages

Every stage that has a field of type OperationContext*
should be updating it when ::restoreState(OperationContext*) is called.
Otherwise it is retaining a reference to deleted memory.

This bug hasn't surfaced before because:
1. the OperationContext used to be stack allocated, so it would have the
   same address every time
2. mmapv1 doesn't always need to dereference the OperationContext

Closes #781

Signed-off-by: Benety Goh <benety@mongodb.com>
SERVER-14887 Remove user document validation from the storage layer.

User documents are validated in the user management commands, validating them in the storage layer
makes the system less flexible and causes problems with mixed-version replica sets.
SERVER-1424 (re)smoke tag parsing and new test library, v0

Includes:
- Smoke.py options for filtering by jstest tags
- New resmoke.py test utility in v0 alpha
- Lots of example resmoke configurations
- SCons integration for unittests
- Sample tagged jstests
SERVER-13621 Add JS tests for backwards box coordinates
SERVER-14561 Provide a way to get an OperationContext on ReplicationCoordinatorExternalState.

Also, make sure to call Client::initThread as needed in
ReplicationCoordinatorExternalStateImpl and NetworkInterfaceImpl.
SERVER-15302 Reduce the scope of the CmdResync write unit of work

Otherwise, this causes TempReleases to happen inside of a write unit of
work, which is not allowed.
SERVER-14668 stash recovery unit with ClientCursor
SERVER-15125 refactor IXSCAN stage to avoid doing too much in one work() cycle
SERVER-13635 fixed rocksdb storage engine test to expect BSONCollectionCatalogEntry options
Merge with upstream/master.
SERVER-15311 Never read from admin.system.new_users when looking for user documents.

The master branch no longer needs to support the 2.4-2.6 upgrade process, obviating the need for
this decision making.  Removing it will reduce the likelihood of future errors, and simplifies
storage concurrency control by removing the need for a multi-document atomic read.
Merge with upstream/master
SERVER-14668 DBRead should be acquiring S lock, not X

This fixes a bug introduced in commit
85e785fdce07dbb23b49220f4798f4627cf6af79.
Merge with upstream/master
Disable document level locking in WiredTiger for now.