gr_basic.cpp now clips filled polygons,using the Sutherland and Hodgman algo to clip the poly against a rectangle
Filled polygons are now correctly displayed under Linux(i hope)

Dialog track options redesigned with wxFormBuilder Alt via drill renamed Specific via drill. Added tips in dialog.

Prevent drawing center from moving when client zoom size exceeds drawing size.
Prevent drawing refresh when zoom level doesn't change to eliminate flicker.

minor changes in search paths for help and translation files.

Mandatory in Pcbnew to handle without error metric grid used now for some footprints (BGA, connectors)
Not fully tested

Comments added in some functions.

Integrate wxFileHistory, add missing header files to fix Linux build, initial search path work, and general housekeeping.

eeschema: code cleaning, comments added, and the true number of sheets and sheets numbers in complex hierarchies