conlang: Rename literals; split, compose, and document Rules

- Renamed literal Types to reflect their literal nature
  - This allows for consistent naming across future non-literal Types
- Complicated lexer Rules have been split into composable sub-rules,
  and moved into the Rule struct.
  - This improves modularity, and allows sharing of sub-rules across rules.
- Documented each lexer rule with (at least) a one-line blurb
  describing its function

dummy.cl

@@ -1,4 +1,9 @@
 #!/ this is a shebang comment!
 // This is an example Conlang file.
 
-/* Conlang supports block comments! */
+/* Conlang supports block comments! */
+ident  // Identifier
+.1     // literal float
+0.1    // literal float
+0x1234 // literal integer
+"str"  // literal string