Tuple support

[dazld]

I couldn't see an option to allow defining tuples as yet - it's not a huge issue, as can combine raw schema data with datofu calls, but using the same DSL would be nice for consistency.

Something like..

(attr :line/point :tuple :index [:double :double]) ;; etc etc


;; which would be the same as
{:db/ident :line/point
 :db/index true
 :db/valueType :db.type/tuple
 :db/tupleTypes [:db.type/double :db.type/double]
 :db/cardinality :db.cardinality/one}

If you're taking PRs, I could give adding the above a go?