Add richard's changes to scemi interface

Richard managed to get past the problems I was having with not getting
responses from the device when run with large images. Here's what he
says:

But, I did make some progress. I notice that if you don't call reset, or
  clear, or done in the test bench, it appears to work fine. I suspect
the
  problem is with these SceMi ports of type 'void'.

  I removed the reset transaction entirely from your design, and
replaced the
  im_clear and im_done transactors with a single transactor of Bit#(1)
which
  sends 0 for m_clear and 1 for im_done. This seemed to fix the issue.

  My updated SceMiLayer and Tb.cpp are attached. I also changed how the
  displacement responses are received, but I don't think you need to
change
  that from what you were doing before.
Merge branch 'master' into ruhler-scemi-update
switch back to non-blocking displacement get
Merge branch 'ruhler-scemi-update' of https://github.com/rdeits/adaptive-PIV into ruhler-scemi-update
outport queue
Merge branch 'ruhler-scemi-update' of https://github.com/rdeits/adaptive-PIV into ruhler-scemi-update
feedback on image packet write
add results from fully functional 640x480 design