* Use FPID instead of wxString in MODULE object.
* Use FPID instead of wxString when loading and saving files.
* Use FPID in COMPONENT object.
* Add wxString helper functions and comparison operators to FPID.
* Add fp_lib token to pcb and netlist file formats.
* Add code to load and save FPIDs to pcb file format.
* Fix segfault when deleting invalid footprint library tables in Pcbnew
  in non footprint library table build.
* Fix bug when counting the number of mod files in
  EDA_APP::SetFootprintLibTablePath();