proper logging, add signal handler for graceful termination

nicoscache.py

@@ -1,4 +1,5 @@
 import re
+import logging
 from ast import literal_eval
 from streams import Stream
 from secop import EnumConvert
@@ -154,7 +155,7 @@ class NicosStream(Stream):
             if self._init:
                 raise TimeoutError('timeout receiving initial values')
         except Exception as e:
-            print(self.uri, repr(e))
+            logging.exception('nicos %r', self.uri)
             return
         for ts, devname, param, op, value in sorted([t, d, p, o, v] for (d, p), (o, v, t) in events.items()):
             descr = self.descr.get(devname)