Use cbvalvw/cbvexvw when sufficient (#2742)
Use cbvalvw/cbvexvw when sufficient (#2742)

* replace use of cbvexv with use of cbvexvw when sufficient (which is almost always the case since it is used with dummy variables)

* add cross-references cbvalvw/cbvalv

* replace use of cbvalv with use of cbvalvw when sufficient (which is almost always the case since it is used with dummy variables)

* make some -labels match the corresponding -labels

* mathbox: bj-bm1.3ii

* minor comment edits, mainly citations
metamath/set.mm,metamath/set.mm,metamath/set.mm