Updated computeGaugeForceQuda so that the coefficients for the action
paths are passed in as an array of doubles rather than a void* array.
Added all the staggered milc-interface code into lib/milc_interface.cpp
Added the milc-interface code for the clover force.
Moved the clover inverter routines into the milc interface.
Still requires some polishing.
Updated the staggered inverter and fattening interface to keep the
fat and long links persistent. An earlier implementation of this
did not check to see that the fat and long-link calculation had been
performed on the device and gave incorrect results
if the link fattening was done on the host instead.
Now, the code only implements persistent gauge fields if
the link fattening is done on the device.

Also added some necessary header files.