gbz80disasm now reads baserom.sym (optional) and gbhw.asm (optional).

This should help cut down on the confusion between the "config" module
and the "config" variable that everyone likes to use. The config
variable should refer to an instance of Config, whereas before it was
being shared as both the name of the module and the name of an instance.

"configuration" is always the module. "config" should always be a Config
instance.

TODO: avoid passing around a Config instance everywhere.

For whatever reason, this makes gbz80disasm work with pokered.

gbz80disasm now uses configuration to determine which files to load
before disassembling a chunk of bytes.

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