Closes #3 Validate DBC frame definitions and report error locations

dbc_parser.h

@@ -39,6 +39,7 @@ class DbcParser {
      * @param filePath Path to input file.
      * @return Parsed database.
      * @throws std::runtime_error on file or parse errors.
+     * Line parse errors include the file path and one-based line number.
      */
     DbcDatabase ParseFile (const std::string &filePath) const;