OCaml: Handle some edge cases; refactor parser, main.ml; add config fetcher

ocaml/lib/parsers/config/fetcher.ml

@@ -0,0 +1,14 @@
+let fetch ?clean (origin: Schema.schema): Schema.schema =
+    let config = Lexer.read origin.meta.defaults.paths.configuration
+    |> Lexer.scan
+    |> List.concat
+    |> Parser.parse
+    in
+
+    if Option.value clean ~default:false then {
+        Schema.origin with input = {
+            origin.input with configuration = {
+                origin.input.configuration with main = config
+            }
+        }
+    } else Parser.apply origin config