revamp the whose phasta BC system

The enormous previously unaccounted-for
complexity of comp1/comp3 conditions is coded
in phConstraint.cc, and the whole system
now acts based on model entities instead of
mesh entities, which in turn should make
the ordering of essential BC nodes consistent
with older phParAdapt versions.
make boundary blocks for all faces

getBCFaces was actually not accurate enough,
it would give faces that had non-natural conditions.
I think the behavior should actually be boundary
blocks for all faces, so just change all the code
to do that and ditch getBCFaces.
fix size of essential BC array