Merge DDR4/ and DDR3/ into a single framework

framework/DDR4/Arbiter.v

framework/DDR4/Bank.v

framework/DDR4/Commands.v

framework/DDR4/ExtractionFIFO.v

framework/DDR4/ExtractionTDM.v

framework/DDR4/FIFO.v

framework/DDR4/Requestor.v

framework/DDR4/Requests.v

framework/DDR4/System.v

framework/DDR4/TDM.v

framework/DDR4/Trace.v

framework/DDR4/Util.v

framework/DDR4/_CoqProject

framework/DDR4/makefile

framework/DRAM/Arbiter.v

framework/DRAM/Bank.v

framework/DRAM/Commands.v

framework/DRAM/FIFO.v

framework/DRAM/FIFO_extraction.v

framework/DRAM/FIFO_proofs.v