swish and mish activation functions

[rijobro]

Description

Swish and Mish activation functions.

Status

Ready

Types of changes

• Non-breaking change (fix or new feature that would not break existing functionality).
• New tests added to cover the changes.
• Integration tests passed locally by running ./runtests.sh --codeformat --coverage.
• Quick tests passed locally by running ./runtests.sh --quick.
• In-line docstrings updated.
• Documentation updated, tested make html command in the docs/ folder.

[wyli]

thanks! could you please also update monai/networks/blocks/__init__.py with the new classes? and perhaps docs/source/networks.rst

[rijobro]

@wyli done, thanks!

[wyli]

/integration-test
(testing the integration command)

[drbeh]

It seems that it the integration command works! Yay! But please let me know if you find any problem with that.