implement POST /api/user and DELETE /api/user/:id api functions along with unit tests.  also updated a few /api/user/* functions to enforce filtering to :is_active true

allow `Field.special_type` to be unset via API 

 Redirect to setup if a setup token still exists

automatically open setup URL when installing metabase 

 automatically infer the special_type of a Field

fix mongo driver connection w/ passwords 

 check for valid DB connection before update in admin

fix paths

retarget the readme from being targetted to contributors to being target...

new setup flow

 Show empty tables in explore

Cast values that filter against mongo _id columns to bson.ObjectId

fallback to :UnknownType for Fields of an unknown type 

generic SQL native QP