new bug report from fmoore
Fixed bug of fmoore (bugs/mike/0-fmoore-pfaffians-res-crash.m2) (part 1)

The bug is one in creating the 'comb' tables, as the memory alloc
in array_class is flawed.  That whole class is flawed, so I rewrote
the comb class, calling it 'Subsets'.  Once 'comb' is eradicated, then
I can delete the array_class class too.

BUT: a bug surfaced that has apparently been a problem for awhile:
exterior power of a Schreyer free module crashes.  Not fixed yet.
fixed schreyer order exterior bug
Fixed bug of fmoore (part 2): add in Subsets class, remove comb

Also removed array_class, which was causing the bug in question: it was
using placement new in incorrect logic.  But this class was a hack
anyway, so it is good to be rid of it.
Changed resolution code in a way that should not be noticeable.

The change only affects "do_by_level>0", which is not documented.  Also
added in a new wish list file for betti numbers
Merge branch 'master' of github.com:Macaulay2/M2