gfse: grammars can now contain one-line descriptions

Also fixed two small problems with public grammars.

src/www/gfse/gf_abs.js

@@ -9,6 +9,7 @@ type FunId = Id -- function name
 type Type = [Cat] -- [Cat_1,...,Cat_n] means Cat_1 -> ... -> Cat_n
 
 type Grammar  = { basename: ModId,
+                  comment: String,
                   extends: [ModId], -- in 1-to-1 correspondence with uextends
 		  uextends: [UniqueId], -- added 2012-10-16
                   abstract: Abstract,