SERVER-10670 Templatize the RoleNameIteratorImpl for std containers.
SERVER-10670 Add setPrivileges and setRoleData methods to User.
SERVER-10670 Expose more parsing functionality from user_management_commands_parser.cpp
SERVER-10670 Maintain role graph consistency.

Keeps the RoleGraph up to date in mongod, and converts MongoS to simply
ask the config server for required information about users and roles.

Performs somewhat aggressive cache invalidation of the users cache in mongod.
Still no cache invalidation in mongos.