method examples; well-formed; inlining all folds

- all folds inferred by heapSatWithFolds should be inlined, rather than
  hoisted out, since the simple check for hoisting doesn't take into account
  whether the fold will have an effect on previously checked expressions.
  for example, for the pattern xs.sum(xs), hoisting the fold out will lead
  to an infinite loop, since it will be unfolded again before the field read.

- also calling heapSatWithFolds at application rule, inlining folds around
  last argument

- type well-formedness

- renamed STyAbbrev to SMuAbbrev

- added sugar for var initializers to parser and printer

      var x = e;  ===  var x; x = e;

- mapHeap, mapMuType, mapRecdType

- in general, don't want to check in all *.n.is files. but want to check in some
  to know when translation mode inserts casts, folds, etc. so added the
  *._.is prefix which runs in translation mode with a dummy index. and the git
  repo will include these files.