[PATCH] allow concat function in mapcss expressions

[cmuelle8]

• allow concat(Object... args) in mapcss to enable composing freeform labels
• word split the string in Label Composer
  • if a word is a key for the prop, substitute the value
  • else append the word as is

e.g.

text: eval(concat("smoothness -- ", "surface"));

will render something like "bad -- asphalt" if the tags are set accordingly.

Greetings

cmuelle8