Initial parse of Sets/*.set

doc/formats/sets.md

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+# Set format information
+
+`*.set` files seem to act as a palette of objects for a [`.map`](maps.md) file.
+The map file loads a set, and can then reference objects by a small number.
+
+Since a maximally-filled map file seems to be able to reference 91,000 * 4
+objects, this is a necessary optimization for 1998-era hardware.
+
+## Structure
+
+These files are plain-text.
+
+We handily have a `template.set`, which looks like:
+
+```
+set template
+
+Defs
+
+40 40 40 80
+
+
+dirt
+h_dirt
+rocks
+blank
+blank
+blank
+blank
+blank
+blank
+blank #
+blank
+blank
+blank
+blank
+blank
+blank
+blank
+blank
+blank
+# ...
+```
+
+The files are of varying lengths. `template.set` is 220 lines, `map10.set` only
+83.
+
+So it's a line-based format that goes:
+
+* Set description
+* Blank line (optional, missing in `GEN_JUN.set`, `GEN_WAS.set`, others)
+* `Defs`
+* Blank line
+* 4 space-separated numbers, variable between sets
+* At least one blank line, sometimes 2
+* A list of object names, sometimes with # comments on the right hand side
+* They all seem to end with a comment of some sort, e.g. `# meaningless comment`
+
+Questions:
+
+What are the `Defs` for? Is it `Defaults` or `Definitions`? The values are
+quite variable between files.
+
+Is whitespace significant in the list of objects? First assumption is no.
+
+Is it a simple 0-indexed palette or do maps embed an absolute line number?
+
+Do positions in the palette have special meaning? e.g. is a particular range
+always reserved for walls?
+
+Are there any special values that don't appear as files in the `Obj/` directory?
+`blank.obj` exists, so I expect not.
+
+Once the map format is fleshed out a little more, can investigate by creating a
+map with a single object from the set in it and seeing what line that works out
+to be.
+