Parking preset icon should be recognizable regardless of language

[1ec5]

The Parking Lot preset has an icon that consists of the letter “P”, for “parking”: . This icon isn’t recognizable in all languages and countries. For example, in Latin America, the equivalent symbol is an “E” for the Spanish estacionamiento or Portuguese estacionamento, while in Spain and Portugal it’s a “P”, per the Vienna Convention.

A more universally recognizable icon would be a car , for consistency with the Bicycle Parking and Motorcycle Parking icons. However, is very appropriate in many languages and countries, so perhaps there should be a way for translators to define a letter that works best in a specific Transifex locale.

This same icon is being added to the Parking Space preset in #5340.

[bhousel]

I changed the icon from a to a