* Encapsulate file name member of base screen object.
* Encapsulate associated screen member of schematic sheet object.
* Create add screen method to schematic sheet object to simplify setting
the associated screen.
* Move the change file name code in the schematic sheet object to the edit
sheet method in the schematic editor frame object to eliminate message
dialogs.
* Improve reference counting in schematic screen object.
* Add helper type definitions for changing schematic object storage to C++
containers.
* Moved ReturnLayerName() to static BOARD::GetDefaultLayerName() and migrated
to a Specctra DSN compatible default layer naming scheme:
Component becomes Front, Copper becomes Back.
* set_color.h: Cmp becomes Front, Cu becomes Back.
* D_PAD::DisplayInfo() changed to use actual copper layer names.
* more layer setup dialog work, moved all programmatic wxControl instantiation
into the wxFormbuilder environment, but this is fraught with danger:
wxFlexGridSizer used the tallest control to establish the row heights, so
be careful about changing control borders in the scroll panel. The vertical
size can explode since just a couple of pixels times the number of rows
is substantial. Currently I am setting a 5 pixel border only left, top, and right
but not bottom.
* Set copper layer count is back in place as a hack until I can get the enabled
layer bit map fully operational.