Added function to print out the JSON header and footer to the backend for...

Added function to print out the JSON header and footer to the backend for parsers that don't use SimpleMatchers.

common/python/nomadcore/baseclasses.py

@@ -346,6 +346,14 @@ class AbstractBaseParser(with_metaclass(ABCMeta, object)):
             default_units=self.parser_context.default_units,
             metainfo_units=self.parser_context.metainfo_units)
 
+    def print_json_header(self):
+        self.super_backend.fileOut.write("[")
+        uri = "file://" + self.parser_context.main_file
+        self.backend.startedParsingSession(uri, self.parser_context.parser_info)
+
+    def print_json_footer(self):
+        self.super_backend.fileOut.write("]]\n")
+
     @abstractmethod
     def parse(self):
         """Used to do the actual parsing. Inside this function you should push