Config file

I've decided to use XML (or a subset of XML) for saving settings to a text file.

Some notes:
- XML is able to save hierarchical information
- Major & minor numbers no longer need to be specified (program should do this automatically)
- Priority for HTB classes does not need to be specified (priority decreases for each additional class)
- Indentation will be ignored and probably not used by the program

Example file:

After looking into the GLib Simple XML Subset Parser, I think it would probably be easier to write my own parser.