core: Add Acquisition Interface

+ Adds first implementation for the Acquisition interface, split into
  Controller and Channel Modules
+ frappy_demo: adds an example simulation
+ new property AttachedDict for a collection of attached modules
+ move Attach and AttachDict to a new file frappy/attached.py
+ interface_classes creation changed. includes now also Acquisition

Change-Id: I198a96065a65bb28f73e468ce0465fca2d8734d7

frappy_demo/test.py

@@ -53,6 +53,7 @@ class WithAtt(Readable):
     def read_value(self):
         return self.att.read_value()
 
+
 class LN2(Readable):
     """Just a readable.