config: Write out config headers in sections

Make the header sections in local.conf and bblayers.conf easier
identifiable by naming them and writing them in chunks, separated by
blank lines. This can help with debugging the resulting configuration.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

kas/config.py

@@ -150,17 +150,26 @@ class Config:
                               self._config.get('target',
                                                'core-image-minimal'))
 
+    def _get_conf_header(self, header_name):
+        """
+            Returns the local.conf header
+        """
+        header = ''
+        for key, value in self._config.get(header_name, {}).items():
+            header += '# {}\n{}\n'.format(key, value)
+        return header
+
     def get_bblayers_conf_header(self):
         """
             Returns the bblayers.conf header
         """
-        return '\n'.join(self._config.get('bblayers_conf_header', {}).values())
+        return self._get_conf_header('bblayers_conf_header')
 
     def get_local_conf_header(self):
         """
             Returns the local.conf header
         """
-        return '\n'.join(self._config.get('local_conf_header', {}).values())
+        return self._get_conf_header('local_conf_header')
 
     def get_machine(self):
         """