Initial file parallelization of all the dslash operators.  Not yet working in multi-gpu.
Merge branch 'quda-0.7' into build_parallel_dslash
Multi-gpu dslash now building for all dslash types.
Removed need for spinor and clover stride constants -  now members of DslashParam and PackParam structs.  Fixed bug when calling commDim in dslash_pack.cu.  Multi-GPU dslash should now work (not yet fully tested).
Staggered dslash test defaults to improved staggered (QUDA_ASQTAD_DSLASH), instead of incorrectly defaulting to Wilson.
Fixed warning message regarding conflict between LatticeField::gather and ColorSpinorField::gather.
Pack commDim now set through an interface function setPackComms() for increased robustness.
Clover stride should only be set when clover field pointers are non-zero.
Removed legacy initSpinorConstants and initCloverConstants functions.
dimFromFaceIndex param struct should be passed by reference.
Only build copyClover if GPU_CLOVER_DIRAC is defined.
Worked around staggered dslashParam scoping issue, and some small clean up.
face_num and face_idx computation in packing kernels moved into if-else block to avoid register spilling.
Fixed bug in pack kernel tuning: added missing metadata such that different commDim values lead to distinct tuneKey values.
Merge branch 'build_parallel_dslash' into quda-0.7