* Add s-expression Format() function to all objects derived from
BOARD_ITEM.
* Add s-expression Format() function to base objects as required.
* Add functions to convert coordinates from base internal units
(nanometers) to millimeter string for writing to s-expression
file.
* Add temporary dummy conversion functions to prevent link errors
until schematic and board object and action code can be separated
into DSO/DLL.
* Add CMake build option to build Pcbnew with nanometer internal
units.
jean-pierre charras
Lorenzo Marcantonio
Craig Southeren
Wayne Stambaugh
Dick Hollenbeck