Add several more FIXME comments with questions and suggestions.

Add some comments and a number of FIXME comments with questions, and
suggestions.

Feme t13: fix indexing of coordinates

feme: t13 updated for multiD coord vectors

feme: added ndof to basis, ndof per node

feme: cleaned up BasisApply

Feme: sketch Operator implementation (incomplete)

Feme: add basic QFunction support

Feme: add gcc/clang/intel dependencies

FemeBasisEval: support arbitrary dim and add t13-basis.c

Feme t12: trivial cleanup

Feme t11-basis: do comparison as part of test

FemePowInt: utility for integer powers

feme: BasisApply big rewrite

FemeBasis: Add reference implementation of basis apply

Written in terms of a tensor contraction. This breaks t11-basis because
it doesn't include 2D yet.

FemeBasis: store interp1d, grad1d in row-major ordering

For consistency with higher rank tensors. Implementations may transpose
internally.

FEME: BasisAply fixed vtemp allocate

Feme: add failing t12-basis.c

FemeBasisApply appears to be incorrect for nonsquare basis application.

FemeBasisApply: const correctness

Feme tap.sh: print output when there is no reference file

Feme: higher d BasisApply for interp

local merge

FEME: first version BasisApply

Feme test: add comparison to reference output

FEME: interp1d, grad1d update, Fornberg 1998