Rewrite config system.

Configuration is rewritten according to Tuukka's vision possibly spiced
up with some of my mistakes. The idea is to have default settings
overridden by area-specific settings in config.coffee. On top of that
one can specify deployment or testing specific settings in
local_config.coffee. A template for the latter is provided.

If local_config.coffee does not exist, the browser can't load
local_config.js and will move on.
Read URLs from config.
Read icons and colors from config.
Read map layer information from config.
offline: include from and to for walk legs