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

ocaml/lib/system/file.ml

@@ -1,3 +1,5 @@
+open Utilities.Aliases
+
 let read_channel channel =
     let buffer = Buffer.create 4096 in
     let rec read () =
@@ -8,6 +10,12 @@ let read_channel channel =
     in
     try read () with End_of_file -> Buffer.contents buffer
 
+let can_read (path: string): bool =
+    try Unix.access path [Unix.R_OK]; true
+    with Unix.Unix_error _ ->
+        elog $ "Failed to read file " ^ path;
+        false
+
 let read path =
     let channel = open_in path in
     read_channel channel