pcb-rnd 3.1.7
~~~~~~~~~~~~~

This release features a lot of bugfixes, a major new feature and
a lot of code removal; highlights:

- major new feature: Rubber Band Stretch Routing; see demos videos at:
  https://archive.org/details/rbs_routing_demo1
  https://archive.org/details/rbs_routing_demo2
  https://archive.org/details/pcb-rnd-rbss-demo3

- removed plugin ar_cpcb; cpcb was not supported by upstream and we have
  a better option in route-rnd

- removed hardwired layer hotkeys - use user configured ones (from layer
  attributes) instead; see
  http://repo.hu/cgi-bin/pool.cgi?project=pcb-rnd&cmd=show&node=deprecation#layerk

- removed the half-finished sketch_route plugin, in favor of the new
  Rubber Band Stretch Routing feature

- support for curved polygon contour in io_eagle
