added PPMS driver

this is driver for the PPMS of LIN at PSI.
This includes the SCoP driver and a simulation, which mimics a
PPMS device including the command interface.
The (small) interface to the windows system of PPMS follows in
a separate patch.

Change-Id: I92173b6dd83016fd1db446c710af101d436fc57b
Reviewed-on: https://forge.frm2.tum.de/review/c/sine2020/secop/playground/+/21445
Tested-by: JenkinsCodeReview <bjoern_pedersen@frm2.tum.de>
Reviewed-by: Markus Zolliker <markus.zolliker@psi.ch>

etc/ppms.cfg

@@ -0,0 +1,123 @@
+[node PPMS.psi.ch]
+description = PPMS at PSI
+
+[interface tcp]
+type = tcp
+bindto = 0.0.0.0
+bindport = 5000
+
+[module tt]
+class = secop_psi.ppms.Temp
+.description = main temperature
+.iodev = ppms
+
+[module mf]
+class = secop_psi.ppms.Field
+.description = magnetic field
+.iodev = ppms
+
+[module pos]
+class = secop_psi.ppms.Position
+.description = sample rotator
+.iodev = ppms
+
+[module lev]
+class = secop_psi.ppms.Level
+.description = helium level
+.iodev = ppms
+
+[module chamber]
+class = secop_psi.ppms.Chamber
+.description = chamber state
+.iodev = ppms
+
+[module r1]
+class = secop_psi.ppms.BridgeChannel
+.description = resistivity channel 1
+.no = 1
+value.unit = Ohm
+.iodev = ppms
+
+[module r2]
+class = secop_psi.ppms.BridgeChannel
+.description = resistivity channel 2
+.no = 2
+value.unit = Ohm
+.iodev = ppms
+
+[module r3]
+class = secop_psi.ppms.BridgeChannel
+.description = resistivity channel 3
+.no = 3
+value.unit = Ohm
+.iodev = ppms
+
+[module r4]
+class = secop_psi.ppms.BridgeChannel
+.description = resistivity channel 4
+.no = 4
+value.unit = Ohm
+.iodev = ppms
+
+[module i1]
+class = secop_psi.ppms.Channel
+.description = current channel 1
+.no = 1
+value.unit = uA
+.iodev = ppms
+
+[module i2]
+class = secop_psi.ppms.Channel
+.description = current channel 2
+.no = 2
+value.unit = uA
+.iodev = ppms
+
+[module i3]
+class = secop_psi.ppms.Channel
+.description = current channel 3
+.no = 3
+value.unit = uA
+.iodev = ppms
+
+[module i4]
+class = secop_psi.ppms.Channel
+.description = current channel 4
+.no = 4
+value.unit = uA
+.iodev = ppms
+
+[module v1]
+class = secop_psi.ppms.DriverChannel
+.description = voltage channel 1
+.no = 1
+value.unit = V
+.iodev = ppms
+
+[module v2]
+class = secop_psi.ppms.DriverChannel
+.description = voltage channel 2
+.no = 2
+value.unit = V
+.iodev = ppms
+
+[module tv]
+class = secop_psi.ppms.UserChannel
+.description = VTI temperature
+enabled = 1
+value.unit = K
+.iodev = ppms
+
+[module ts]
+class = secop_psi.ppms.UserChannel
+.description = sample temperature
+enabled = 1
+value.unit = K
+.iodev = ppms
+
+[module ppms]
+class = secop_psi.ppms.Main
+.description = the main and poller module
+.class_id = QD.MULTIVU.PPMS.1
+.visibility = 3
+pollinterval = 2