#58 Customizable menu colors

[Uwe]

Customizable colors for menus (the user has then more opportunities than the standard grey
in grey menu). Set and store the menu colors in the options menu like the fonts.
Use
option add MenuBackground $color...
option add MenuForeground $color...
option add MenuactiveBackground $color...
option add MenuactiveForeground $color...
option add MenuselectColor $color...
to set the menu colors global