Properly initialize settings dir

Since config.yaml gets now saved on server startup before settings basedir gets initialized by other means (e.g. first access of base folder for uploads), it was not created yet when the config.yaml was tried to be saved upon first start up, causing an error at server startup.

Closes #604

src/octoprint/settings.py

@@ -181,6 +181,9 @@ class Settings(object):
 		else:
 			self.settings_dir = _resolveSettingsDir(APPNAME)
 
+		if not os.path.isdir(self.settings_dir):
+			os.makedirs(self.settings_dir)
+
 	def _getDefaultFolder(self, type):
 		folder = default_settings["folder"][type]
 		if folder is None: