Improve element/node data type representation

[grtjn]

node() and element() are likely not recognized as-is. Need to debug sjs to see what MarkLogic uses internally.. (suggestions welcome)

[grtjn]

Comparing types listed on DMC itself. Unfortunately, a lot of detail gets lost when sequences are returned as ValueIterator..

[grtjn]

DMC is deriving this from the current XML as well, see for instance here:

https://github.com/marklogic/RunDMC/blob/master/src/apidoc/model/data-access.xqy#L782

[grtjn]

Those datatype mappings don't look as really been validated. Integer should be number, null should be void.

[grtjn]

Made a large step forward, but DMC style for describing arguments doesn't match typescript/javascript syntax. Nor seem many types very accurate. Is something like cts.period a correct type? If so we need to add a list of such object defs statically maybe..