a series of regfiles are needed, with different characteristics and a common API
added XER and CR based on new VirtualRegPort.
INT and FAST also added, based on RegFileArray
that just leaves SPRs which are massive. may leave that for now.
added SPRMap which translates to internal enum mapping in hardware.
SPR was added as binary-addressed, alongside SPRmap. aside from dec and tb the regfiles are now in place.