core: Triggers can now frobid other triggers execution

if a trigger raise SkipOtherTriggers exception, normal behaviour will occure, skipping other triggers

src/tools/misc.py

@@ -26,6 +26,11 @@ from logging import debug, info, error
 class TriggerException(Exception):
     pass
 
+class SkipOtherTriggers(Exception):
+    """ Exception to raise if normal behaviour must be followed instead of
+        followind triggers list """
+    pass
+
 class TriggerManager:
     """This class manage triggers: code which interact to change de behaviour of SàT"""
 
@@ -62,7 +67,10 @@ class TriggerManager:
             return True
 
         for priority,trigger in self.__triggers[point_name]:
-            if not trigger(*args, **kwargs):
-                return False
+            try:
+                if not trigger(*args, **kwargs):
+                    return False
+            except SkipOtherTriggers:
+                break
         return True