add generic Mac toolchain file

I prefer that CMake find the MPI compiler wrappers instead of the base
compilers, if for no other reason than this often means mixing clang and
gfortran, since clang will likely be found first in PATH.

this toolchain assumes MPI wrappers are in the PATH but one can set the
base directory (with a trailing "/") if desired.

the BLAS/LAPACK used is "-framework Accelerate"
Finishing migration to static instantiation of all level1 BLAS routines (with the exception of EntrywiseMap).
Merge branch 'master' of https://github.com/elemental/Elemental
Fixing mistakes in [VC,STAR] Gemv and avoiding several unnecessary manual redistributions in BLAS2 routines.
Statically instantiatiing level2 BLAS.
With the exception of EntrywiseMap, all BLAS routines are now statically instantiated. The reason is that, in order to support C/Python/R/etc interfaces to Elemental, the library must be statically instantiated, and so the remaining routines in Elemental will soon be moved into src/ as well.
condense/ and factor/ are now statically instantiated.
Moving funcs/ into src/
Statically instantiating lapack-like/util/ and moving permutation routines into lapack-like/perm/
Moving lapack-like/perm/ into src/
Moving lapack-like/solve into src/
Moved lapack-like/decomp/ into src/
Moving all of lapack-like/props/ tino src/ with the exception of Pseudospectrum
Statically instantiating Pseudospectrum
Fixing several static instantiation issues for lapack-like and beginning to add a test driver for a quadratic-program-based non-negative least squares.
renaming convex/ to optimization/, statically instantiating it, and fixing a mistake in the ADMM QP solver. The non-negative least squares solver now agrees with the results from lsqnonneg.
Making NonNegativeLeastSquares a routine and fixing mistakes in in-progress distributed k-means implementation.
Extending QP and NNLS to handle multiple right-hand sides in an efficient way and adding a Non-negative Matrix Factorization (NMF).
Statically instantiating control/ and avoiding compiler warnings in AxpyInterface due to sendDummy_ and recvDummy_ not being initialized.
Adding an (untested) LASSO implementation and a missing instantiation of Conjugate which was preventing the BunchKaufman example driver from linking.