implement configurable module-properties

+ make parameter-properties configurable
+ better derivation of automatic properties
+ implement 'group' properties (how to display in gui???
+ clean up descriptive data by omitting unset and live properties

Change-Id: Icd2b6e91e09037e9d4a8d6ad88483f8509a2cf5f

etc/cryo.cfg

@@ -11,7 +11,12 @@ encoding=demo
 
 
 [device cryo]
+# some (non-defaut) module properties
+.group=very important/stuff
+# class of module:
 class=devices.cryo.Cryostat
+
+# some parameters
 jitter=0.1
 T_start=10.0
 target=10.0
@@ -27,3 +32,6 @@ tolerance=0.1
 window=30
 timeout=900
 
+# some (non-default) parameter properties
+pollinterval.export=False
+