basic config support
class Preprocessor instead of just functions
make wram.py use config for paths

The WRAMProcessor class handles reading all constants and labels, which
are then used in gbz80disasm.
make gbz80disasm use configuration

gbz80disasm now uses configuration to determine which files to load
before disassembling a chunk of bytes.
Merge pull request #10 from kanzure/config

Configuration for paths