Closes #71: Allow cross-origine for Google calendar compatibility

tracim/development.ini.base

 # radicale.server.port = 5232
 # radicale.server.ssl = false
 # radicale.server.filesystem.folder = ~/.config/radicale/collections
+# radicale.server.allow_origin = *
 ## url can be extended like http://127.0.0.1:5232/calendar
 ## in this case, you have to create your own proxy behind this url.
 # radicale.client.base_url = http://127.0.0.1:5232

tracim/tracim/config/app_cfg.py

             'radicale.server.filesystem.folder',
             '~/.config/radicale/collections'
         )
+        self.RADICALE_SERVER_ALLOW_ORIGIN = tg.config.get(
+            'radicale.server.allow_origin',
+            '*',
+        )
 
         self.RADICALE_CLIENT_BASE_URL_TEMPLATE = \
             tg.config.get('radicale.client.base_url', None)

tracim/tracim/lib/daemons.py

         tracim_rights = 'tracim.lib.radicale.rights'
         tracim_storage = 'tracim.lib.radicale.storage'
         fs_path = cfg.RADICALE_SERVER_FILE_SYSTEM_FOLDER
+        allow_origin = cfg.RADICALE_SERVER_ALLOW_ORIGIN
 
         radicale_config.set('auth', 'type', 'custom')
         radicale_config.set('auth', 'custom_handler', tracim_auth)
         radicale_config.set('storage', 'custom_handler', tracim_storage)
         radicale_config.set('storage', 'filesystem_folder', fs_path)
 
+        radicale_config.set(
+            'header',
+            'Access-Control-Allow-Origin',
+            allow_origin,
+        )
+
     def _get_server(self):
         from tracim.config.app_cfg import CFG
         cfg = CFG.get_instance()