Things to tidy up

[tofu-rocketry]

While working on AMS integration, I've noticed the following:

• Remove password and username as they aren't used #219
• use_ssl defaults to False in Ssm2 init #218
• loads of PEP8 violations, including messy import ordering
• import ssl handling can be removed as we support 2.6 upwards (Drop Python 2.6, add Python 3 test compatibility #115)
• configparser and needs handling for Python 3 support (changed names and modules)
• inconsistent file licenses and docstrings

[tofu-rocketry]

To address Python 3 bits for https://github.com/apel/ssm/milestone/23

[tofu-rocketry]

For licences and docstrings, apgents.py has the layout I prefer.