L2SS-200: file restructuring for tango project

This uses the temporary sys.path.append trick to find all project files relative to the root folder even though the mains are scattered across different levels of directory structures. This problem will resolve itself once packaging is in place.

Closes L2SS-200

devices/clients/attribute_wrapper.py

@@ -3,7 +3,7 @@ from tango import AttrWriteType
 
 import numpy
 
-from util.wrappers import only_when_on, fault_on_error
+from devices.device_decorators import only_when_on, fault_on_error
 import logging
 
 logger = logging.getLogger()