Add tools for designing stuff

So, now that devilution is nearly complete, we are missing a few tools that would've been present to help with making stuff. Possible tools to add:

- [ ] CEL/CL2 <-> GIF converter
- [ ] Tabbed text to C header
- [ ] .DUN map creator
- [ ] Base game setup/installer

There are already some existing tools for CEL stuff, but most of them are 10+ years old and didnt provide the source. I already have a working .txt -> .cpp converter, but it needs a bit of safe-proofing before it's good to go.