Debug helpers dumpColl/dumpCollAsItems().
Inefficiently utilize view map-function memoization.

At view query time, rather than executing the JS map function over
every document, the memoized map-function-emits (vindexes) are now
scanned, albeit via an inefficient (but functional) full vindex scan.

A future change will leverage the startkey and endkey to limit the
range of the vindex scan.