Python Syntax for Templated Methods

[kwabenantim]

Summary

Following the nicer Python syntax for templated classes added in #13, it would be good to have nicer Python syntax for templated methods as well.

For example in C++ we have

population.AddCellWriter<CellVolumesWriter>();

In Python this is currently

population.AddCellWriterCellVolumesWriter()

A nicer Python version could be

population.AddCellWriter[CellVolumesWriter]()