Create a new dialog to edit global and project specific symbol library
tables.
Add menu entries for new symbol library table editor in schematic editor
and symbol library editor main frame menus.
Add command event handler for symbol library table editor dialog to
SCH_BASE_FRAME so it is accessible from derived frames.
Fix bug in default environment variables initialization. A test for
existing user defined environment variables was preventing any new
default environment variables added to the list from being initialized.
Wayne Stambaugh