* Remove ENVIRONMENT_VARIABLE_CHAR_VALIDATOR::OnChar() because it was skipping
the filtering of the first character. Not sure what was going but this seemed to fix the issue.
* Added environment variable name test to DIALOG_ENV_VAR_CONFIG::TransferDataFromWindow
because apparently validators do not get called in wxGrids even whe the extend window style
wxWS_EX_VALIDATE_RECURSIVELY is set.
* Set the default button using wxFormBuilder since the OK button is not part of a wxStdDialogButtonSizer.
* Minor improvements to the HTML help dialog.
* Fix assertion when calling HTML help dialog. Apparently any dialog derived from DIALOG_SHIM must
have a KIWAY top level window as a parent.
* Create new dialog to edit environment variables.
* Add helper class ENV_VAR_ITEM to manage environment variable values and
if they were defined externally.
* A path configuration dialog access to KiCad, CvPcb, Pcbnew, and Footprint Editor
window menus.
* Add validator for environment variables.