Pcbnew: Extending IPC (via socket) command set in standalone application execution

Set of processable incoming commands was extended by same in functionality eeschema commands: $PART: "reference" - Highlight footprint $PART: "reference" $PAD: "pin name" - Highlight footprint pin

Added main KiCAD functionality: A first step in full functional cross-probing in standalone mode (via socket, without KiWay)

Alternative functionality: Can highlight footprints and pads from external application