This is *a work in progress*, so some features are missing, and/or could be modified.
Mainly keepout zones are not yet exported to autorouters, and pads are not taken in account.
Some code cleanup in polygon.*
* Derive the pcbnew copper zone and non-copper zone dialog windows from DIAG_SHIM,
which injects some template code.
* Update UIpolicies.txt to talk about DIALOG_SHIM support.
* Add zone support to eagle_plugin.
* Organize ZONE_CONTAINER class declaration for future privacy and accessors.