Some coding style policy fix.

Footprint wizard converts from user units to internal units back and forth, so user can type in mm or mils now

Eeschema: fix a bug that crashes eeschema (only when compiled in debug mode) when creating a new wire, and when any wire orientation is allowed.

Pcbnew: more about keepout areas: remove keepout for pads option and add keepout for copper zones option.
Export keepout to Specctra DSN file.

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.*

Fix incorrect import of smd pads from Gpcb.
Very minor change in dialog print.

Eeschema: bug fix: when creating new connections, junctions were not always automatically added when needed.
Fix an other minor bug.

Add copy to text items in pcbnew. Automatically mirror text items added to back silkscreen (bug 1017446).

Coordinates were using always 3 digits (1/1000 inch  for mantissa). Uses now 4 digits max in inches and 3 digits max in mm
The resolution is therefore 1/10000 inch or 1/1000 mm. Note this is a limitation of Excellon format.

When reading board files, the net 0 was stored twice.
It creates only log messges in debug mode, because the list of nets is rebuild after reading files.