Added golf_course-color to leisure=miniature_golf-areas

Now ways, which are tagged with leisure=miniature_golf get the same
(green) coloring as golf_courses.
Added symbol to minigolf-courses and if available its name also shows up (both at zoom>=17)

The symbol is
http://www.sjjb.co.uk/mapicons/png/sport_minature_golf.p.20.png from http://www.sjjb.co.uk/mapicons/contactsheet#sport
The text has the same color as the name of golf-courses.