Improve CentralRouter and GBT wrapper CDC
Changes added with respect to master:
XVC (Xilinx Virtual Cable) over PCIe (FLX-1914)
Improved reset and settings synchronization and added some XPM_CDC in centralRouter
Added CDC in GBT wrapper. This adds 1 BC latency in the GBT TX path
Made ToFrontend fanout selector combinatorial to compensate for the 1 BC added latency in GBT wrapper.