refactored lexical category inference for {} nodes
enabled some tests which used to fail long ago
prelude: replaced usages of {A}⍠{B} with {A;B}
moved ⍨ to prelude: ⍨←{⍵⍶⍵;⍵⍶⍺} ⍝ beautiful!
Merge remote-tracking branch 'origin/master' into gh-pages
built demo