done adding export-collision functionality, including collision message, in functional core. Next: add imperative shell scaffolding

message-types/file-msg.sml

@@ -4,6 +4,7 @@ struct
     SAVE_SQUARES of string
   | LOAD_SQUARES
   | EXPORT_SQUARES of string
+  | EXPORT_COLLISIONS of string
   | LOAD_FILES of string
   | SELECT_PATH of string
 end

message-types/input-msg.sml

@@ -19,6 +19,7 @@ struct
   | KEY_CTRL_L
   | KEY_CTRL_E
   | KEY_CTRL_O
+  | KEY_CTRL_C
   | NUM of int
   | ARROW_UP
   | ARROW_LEFT