Code cleanup

Here is a patch thats cleans up the mapstraction_style_map.inc a bit.

I rewrote the field mappings, to allow for individual descriptions for each field (which also fixes #439752: Allow different icons). This is increases the readability of the code and the usability of the interface. Profit!

I also fixed some blank lines and some variable names.

It probably had been better to break this up in smaller patches. But I made it this way since there isn't much going on in the issue queue right now.

I have tested it, and will commit it in a few days if someone doesn't disagree.