Refactored ExecutionContext serialization (added sheerkapickle) and added History management

tests/sdp/test_sheerkaDataProvider.py

@@ -257,24 +257,27 @@ def test_i_can_load_events(root):
     for i in range(15):
         sdp.save_event(Event(f"Hello {i}"))
 
-    events = list(sdp.load_events(10))
+    events = list(sdp.load_events(10))  # first ten
     assert len(events) == 10
     assert events[0].message == "Hello 14"
     assert events[9].message == "Hello 5"
 
-    events = list(sdp.load_events(10, 5))
+    events = list(sdp.load_events(10, 5))  # skip first 5, then take 10
     assert len(events) == 10
     assert events[0].message == "Hello 9"
     assert events[9].message == "Hello 0"
 
-    events = list(sdp.load_events(20, 10))
+    events = list(sdp.load_events(20, 10))  # skip first 10, take 20,(but only 5 remaining)
     assert len(events) == 5
     assert events[0].message == "Hello 4"
     assert events[4].message == "Hello 0"
 
-    events = list(sdp.load_events(1, 20))
+    events = list(sdp.load_events(1, 20))  # skip first 20, take one
     assert len(events) == 0
 
+    events = list(sdp.load_events(0))  # all
+    assert len(events) == 15
+
 
 @pytest.mark.parametrize("root", [
     ".sheerka",