- Adding new `Func<DateTime, DateTime?>` that allows PCM to return null
if the next rebalance time is null, in which case the function will be
called again in the next loop.
- Adjusting PCM next rebalance time check to perform rebalance once the
time is reached
- Adding new regression test. Updating existing
- Adding new `CompositeAlphaModel.AddAlphaModel()`
- Adding C#/Py regression algorithms using the new `QCAlgorith.AddAlphaModel()`
- Improving exception message
- Add python version of `QCAlgorith.AddAlphaModel()`