Change in retina parameters: foregroundRate and backgroundRate replace noiseOnFreq and noiseOffFreq. If noiseOnFreq or noiseOffFreq are in the params file, a warning is issued. poissonBlankProb and poissonEdgeProb are obsolete; it is an error to use these parameters instead of foregroundRate/backgroundRate.
Change in retina parameters:
foregroundRate and backgroundRate replace noiseOnFreq and noiseOffFreq.
If noiseOnFreq or noiseOffFreq are in the params file, a warning is issued.
poissonBlankProb and poissonEdgeProb are obsolete; it is an error to use these parameters instead of foregroundRate/backgroundRate.

Also, maxRate is set to foregroundRate, and it is an error to have backgroundRate greater than foregroundRate.

git-svn-id: 602a26e73ae9f2a14e2bb95676f2e137fcc39919@6517 7c0444ca-5550-0410-9008-faecdbe78eb5

PetaVision/OpenPV,dpaiton/OpenPV,dpaiton/OpenPV,dpaiton/OpenPV,dpaiton/OpenPV,dpaiton/OpenPV,PetaVision/OpenPV,dpaiton/OpenPV,dpaiton/OpenPV,dpaiton/OpenPV,PetaVision/OpenPV,PetaVision/OpenPV,PetaVision/OpenPV