Updated RxPortToFile with better code for turning on the receive functions.  Added additional interface definitions to make the code easier to read than looking at cryptic hex codes.   Restructured, so command line arguments should be easy todo with specification of the front end, gain, frequency, path, host rate, etc.  Tested up to a maximum of 8 MSamples per second (32 MBytes per sec) on USB 2.0.  Couldn't test USB 3.0 need to update Linux drivers for that.