dialog plot functions: fix compil warnings with wxWidgets 2.8

Kicad manager: shows now svg files in tree files.
Pcbnew: fix incorrect printing (board out of page) when creating drill map in postscript format ( noticeable mainly for small boards)

3d-viewer and polygon functions: remove duplicate code about conversion from basic shapes to polygons.

Eeschema: annotate and netlist dialogs: enhancements.
Minor  coding policy fixes and  changes.

All: press ctrl+shift key when moving the mouse allows the graphic cursor to be moved outside the grid.
(useful to place graphic objects, texts in any position, regardless the current grid)

pcbnew scripting: cleanup, renamed KICAD_SCRIPTING_EXPERIMENT to KICAD_SCRIPTING_WXPYTHON, now every flavour compiles

Pcbnew: code cleaning in polygons

Remove arcs support in zone outlines: this is a legacy code from FreePCB, never used, never tested, never maintained.

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