Bugfixes and preparation of interfaces. Now it compiles correctly, but the operator is still untested.

- Added the file dirac_twisted_clover.cpp in Makefile.
- Added ASSSN in read_clover.h, and substituted the READs by ASSNs in the dslash and tmc kernels.
- Added interfaces in interface_quda.cpp.
- Added command-line recognition of the new dslash as "twisted_clover".
- Added possibility of testing the dslash with the dslash_test code (UNTESTED!).