For property, use decorator or lambdas.

[anntzer]

Replace

def _get_foo(self): ...
foo = property(_get_foo)

by

@property
def foo(self): ...

or

foo = property(lambda self: ...)

(for the one-liner cases, when there are many of them, allowing to block
them together without blank lines in between).

Remove Affine2D.is_separable -- we can just inherit it from
Affine2DBase.is_separable.

PR Summary

PR Checklist

• Has Pytest style unit tests
• Code is PEP 8 compliant
• New features are documented, with examples if plot related
• Documentation is sphinx and numpydoc compliant
• Added an entry to doc/users/next_whats_new/ if major new feature (follow instructions in README.rst there)
• Documented in doc/api/api_changes.rst if API changed in a backward-incompatible way

[dopplershift]

Trying to decide if I should merge this before 3.0 is branched...