COFFEE supports dense linear algebra libraries

COFFEE can now transform left-hand side kernels into sequences of calls to linear algebra libraries' DGEMM. So far, MKL, ATLAS and EIGEN are supported, and the code can be easily extended to other libraries.

This depends on a Pull Request 46 in mapdes/ffc
opts contains the optimizations requested by the user; _opt_blas tells you if the transformation was successfully applied (i.e. True iff the kernel was amenable to this transformation and the conversion into BLAS calls was successful, False otherwise). I'll add a comment.