Bus_ISA_8bit fix
Created by: nickysn
This pull request contains only a fix for the name of the two ~MEM signals in BUS_ISA_8bit. Previously, there were two signals named ~MEM and it wasn't clear which one is for memory read and which one for memory write. I renamed them ~SMEMW (System Memory Write) and ~SMEMR (System Memory Read), which also makes them consistent with Bus_ISA_16bit.
For some reason, loading and saving the Connector library in KiCad 5.0.0 resulted in various changes to the file. I don't know how to avoid that. I committed this change separately.