rework frappy to be a device instead of a command

+ improve proposed config mechanism

setups/frappy.py

@@ -4,10 +4,8 @@ group = 'optional'
 modules = ['nicos_sinq.frappy_sinq.commands']
 
 devices = dict(
-    frappy_config = device(
+    frappy = device(
         'nicos_sinq.frappy_sinq.devices.FrappyConfig',
-        # frappy_config does not need to be visible
-        visibility = [],
         # the possible SECoP connections
         nodes = ['se_main', 'se_stick', 'se_addons'],
         #
@@ -64,5 +62,5 @@ printinfo("  frappy('')                           # remove main SE apparatus")
 printinfo("  frappy()                             # show the current SE configuration")
 printinfo("=======================================================================================")
 set_se_list()
-frappy_changed()
+frappy.has_changed()
 '''