pcb-rnd 1.2.3
~~~~~~~~~~~~~

Among the usual bugfixes, the following major features have been added:

1. Plugin system rewrite; the original system, mostly consisting of code
inherited from mainline, was unable to handle plugin-plugin dependencies,
couldn't distinguish between "available" and "should load". Switched over
the whole plugin system to puplug.

2. Editable mask and paste layers, using positive/negative, auto/manual
compositing layers. Silk layers can be composite too, with manual-negative
layers removing auto silk generated by elements. (Not yet available with
opengl rendering.)

3. Gtk: new layer selector widget in top window and cross-section view
upgrades to expose the new composite layer features of the editable layers.

4. eagle board import - special thanks to LA3PNA (Thomas S. Knutsen) for
supporting the implementation
