default settings on the IO class

allow to define default settings on the IO class:
- a default 'port' may be given for tcp
- defaults like 'baudrate' or 'parity' might be given
  for serial connections

this avoids explicit settings in the config file in case
the settings can not be changed or have a typical value
other than the defaults in serial.Serial

Change-Id: I990f47d63e785f8cc48c4af197944a8eebe91fb4
Reviewed-on: https://forge.frm2.tum.de/review/c/secop/frappy/+/30555
Reviewed-by: Georg Brandl <g.brandl@fz-juelich.de>
Tested-by: Jenkins Automated Tests <pedersen+jenkins@frm2.tum.de>
Reviewed-by: Markus Zolliker <markus.zolliker@psi.ch>

frappy_demo/lakeshore.py

@@ -32,6 +32,7 @@ class LakeshoreIO(StringIO):
     # Lakeshore commands (see manual)
     # '*IDN?' is sent on connect, and the reply is checked to match the regexp 'LSCI,.*'
     identification = [('*IDN?', 'LSCI,.*')]
+    default_settings = {'port': 7777, 'baudrate': 57600, 'parity': 'O', 'bytesize': 7}
 
 
 class TemperatureSensor(HasIO, Readable):