Major kmeans cleanup

Work-in-progress; "scoring" kmeans still dumps to stdout instead of
json.
Added a KMeans scoring option, and link from the KMeans model-view page.
KMeans has no response column; fixed some OBOB errors.
KMeansModel keys given the "Model__" suffix, so the typeahead will find
it.
Fixed bug with using shallow-clone instead of deep-clone when returning
KMeans results.  Removed dup code in minSqr & closest.  Removed dup code
around calling 'datad' and 'minSqr'.  Added lots of comments.  NULL-out
IN-only variables at the end of map calls.  Added separate "scoring"
function.