Proof of concept for loading cycle list definitions from separate files ...

...using the 'cycle list name' key.

When 'cycle list name' is called, we first check whether that cycle list is already defined. If it isn't, we check whether a file with the cycle list name exists. If it does, we construct the cycle list from that file, using code provided by Christian Feuersänger at http://tex.stackexchange.com/a/32064/2552. If it doesn't, we display an error message.

This is only a proof of concept, only the "YlGn-3" and "Set1-4" cycle lists are defined.