MainFrm: Merge the two add favorite functions, reduces code duplication.
DSUtil: Add versions of Explode() and Implode() with escaping support.
As a simplification, escaping characters are not escaped themselves.
Favorites: Add escaping support to favorites.
Fixes cases where a filename containing a semicolon could not be opened.
FavoriteOrganizeDlg: Brushes should only be created once.
Fixes assert triggering when selecting items.