SERVER-10823 update member configs properly on tags-only reconfigs

fixes problems caused by SERVER-6376
SERVER-10532 add sentinel values for ChunkVersion
SERVER-6246 Small improvements to user management commands parsing.

Make sure that every command gets checked that there are no extra arguments, and be consistent
about where writeConcern is parsed;
SERVER-5916 Allow bare $$ROOT or $$CURRENT without subfields

This represents the whole variable (usually the full incoming document).
Test for SERVER-9289 Date operators taking subexpression directly

The bug was fixed in earlier refactoring of Expression parsing.
SERVER-10026 guard against  throwing by RAII-ifying deregistration for pre-cached runners
SERVER-10026 sort inherits the previous memory limit.  generate ixscan-as-sort plan.
SERVER-10026 add hint and snapshot support