Improving on GUI shapes

[behrisch]

Some shapes look more or less like the default rectangle with rounded shapes. If we don't want to have a specific shape here we should remove them

• [ ] vshape_rail
• [ ] vshape_rail_car
• [ ] vshape_rail_cargo
• [ ] vshape_bus_flexible

Furthermore a rickshaw should maybe look more like a threewheeler

[namdre]

I think rail_cargo and bus_flexible should have a different look. Not sure about rail vs rail_car.