fix two typos

boot.py

@@ -105,7 +105,7 @@ class _MynitConfig:
             print("Wrote configuration to file")
 
     def register(self, name, verbose_name, schema):
-        """Rgister a configuration schema."""
+        """Register a configuration schema."""
         self._schemas[name] = (verbose_name, schema)
 
     def _has_setting(self, schema, setting):
@@ -130,7 +130,7 @@ class _MynitConfig:
         if not self._has_setting(schema, setting):
             raise KeyError("Setting %s in schema %s is unknown." % (setting, schema))
 
-        self._configu.setdefault(schema, {})[setting] = value
+        self._config.setdefault(schema, {})[setting] = value
         self._save()
 
     def __getitem__(self, schema):