my mathbox: elmtwise --> elwise; other: pair-wise --> pairwise, compo… (#2439)
my mathbox: elmtwise --> elwise; other: pair-wise --> pairwise, compo… (#2439)

* my mathbox: elmtwise --> elwise; other: pair-wise --> pairwise, component-wise --> componentwise, for consistency

* typo

* typo

* formatting consistency for section headers

* typos

* relexive--> reflexive and a few more typos
metamath/set.mm,metamath/set.mm,metamath/set.mm