Hiero command line support

Two minimal patches for running Hiero from command line. This for example allows one to create fonts for multiple screen resolutions right from build scripts.

Forum discussion: http://www.badlogicgames.com/forum/viewtopic.php?f=11&t=16422

The settings file has until now ignored the second font (the one loaded from a user-specified file), which has instead been loaded from preferences. This made batch operation impossible (since the hiero could use a different font from the one user had specified) and the first patch fixes that (while still remembering the filename in prefs).