autodoc crashed when a decorator in mocked module takes arguments
because mock system returns the first argument for the decorator as a
decorated object.
This changes the approach for mocking decorators that remembers
arguments for each decoration, and fetch the latest argument on
generating document.
Keep imports alphabetically sorted and their order homogeneous across
Python source files.
The isort project has more feature and is more active than the
flake8-import-order plugin.
Most issues caught were simply import ordering from the same module.
Where imports were purposefully placed out of order, tag with
isort:skip.
