DOCS-2243 adds db.getUser and db.getUsers

Signed-off-by: Sam Kleinman <samk@10gen.com>
DOCS-2244 add tocs for users and roles methods

Signed-off-by: Sam Kleinman <samk@10gen.com>
commenting out non-extant pages
user management redirects for new pages
collect -> identify in tutorial
minor: adding terminate running operations to navigation page