res.cpp: Extract data into XML file

[OnlineCop]

While (still) poring over eResistance and other recent changes, I've found quite a few bugs (yay!). Having a giant wall of data in res.cpp isn't ideal, however.

If I were to move these into the data folder as an XML, it should have an added advantage of allowing the stats to be hot-reloaded via Lua, so we can test that things like spells and elemental attacks are doing what they're supposed to.

If anyone sees disadvantages/cons to this, let's discuss. Otherwise, I think I'll start this migration process.