add lakeshore demo for hands-on workshop

- a simple LakeShore model 336 driver

a tutorial follows

Change-Id: I291a615efa5bd58a0dd908949210086d2f82c2ca

cfg/ls336_cfg.py

@@ -0,0 +1,18 @@
+Node('example_cryo.psi.ch',  # a globally unique identification
+     'this is an example cryostat for the Frappy tutorial',  # describes the node
+      interface='tcp://10767')  # you might choose any port number > 1024
+Mod('io',  # the name of the module
+    'frappy_demo.lakeshore.LakeshoreIO',  # the class used for communication
+    'communication to main controller',  # a description
+    uri='tcp://129.129.138.78:7777',  # the serial connection
+    )
+Mod('T',
+    'frappy_demo.lakeshore.TemperatureLoop',
+    'Sample Temperature',
+    io='io',
+    channel='A',  # the channel on the LakeShore for this module
+    loop=1,  # the loop to be used
+    value=Param(max=470),  # set the maximum expected T
+    target=Param(max=420),  # set the maximum allowed target T
+    heater_range=3,  # 5 for model 350
+    )