new poll mechanism

- remove secop.poller and basic poller
- regular polls for 'important' parameters done by method doPoll
- all other parameters are polled slower (slowInterval) and
  with lower priority (only one at a time when main poll is due)
- nopoll decorator for read_* to disable poll
- enablePoll attribute (default True) for disabling polling a module
- fast polls may be implemented by means of a statemachine
- configurable slow poll interval
+ allow a Parameter to override a Property (parameter
  Readable.pollinterval overrides Module.pollinterval)

Change-Id: Ib1b3453041a233678b7c4b4add22ac399670e447
Reviewed-on: https://forge.frm2.tum.de/review/c/sine2020/secop/playground/+/27832
Reviewed-by: Enrico Faulhaber <enrico.faulhaber@frm2.tum.de>
Reviewed-by: Markus Zolliker <markus.zolliker@psi.ch>
Tested-by: Jenkins Automated Tests <pedersen+jenkins@frm2.tum.de>

test/test_properties.py

@@ -26,6 +26,7 @@ import pytest
 from secop.datatypes import FloatRange, IntRange, StringType, ValueType
 from secop.errors import BadValueError, ConfigError, ProgrammingError
 from secop.properties import HasProperties, Property
+from secop.core import Parameter
 
 
 def Prop(*args, name=None, **kwds):
@@ -149,17 +150,25 @@ def test_Property_override():
     assert o2.a == 3
 
     with pytest.raises(ProgrammingError) as e:
-        class cx(c): # pylint: disable=unused-variable
+        class cx(c):  # pylint: disable=unused-variable
             def a(self):
                 pass
     assert 'collides with' in str(e.value)
 
     with pytest.raises(ProgrammingError) as e:
-        class cz(c): # pylint: disable=unused-variable
+        class cy(c):  # pylint: disable=unused-variable
             a = 's'
 
     assert 'can not set' in str(e.value)
 
+    with pytest.raises(ProgrammingError) as e:
+        class cz(c):  # pylint: disable=unused-variable
+            a = 's'
+
+    class cp(c):  # pylint: disable=unused-variable
+        # overriding a Property with a Parameter is allowed
+        a = Parameter('x', IntRange())
+
 
 def test_Properties_mro():
     class Base(HasProperties):