pcb-rnd 3.1.2
~~~~~~~~~~~~~

This release contains a lot of code cleanup, some feature removal and
a few new features:

1. Code cleanup: remove the dependency on the rtree compatibility layer, use
   librnd native rtrees

2. Feature removal: gsch2pcb-rnd removed and replaced with a dummy that prints
   the alternatives, including CLI and GUI import sch 

3. New 3d models: openscad models for all parametric footprints in the standard
   footprint lib

4. Rewrite of export_bom: BoM export uses user configurable templates instead
   of a hardwired format
