Python3 Update

[StephenBrown2]

Required for moving https://github.com/openaps/openaps to Python3 as the deps are dropping py2 support like hot potatoes.

Significant changes:

• Python3 has no long type, it's all just int, so BangLong now returns an int without the L suffix.
• / now always does float division, while // does Python2-style integer division. Most of the time this is expected, as there is a float somewhere in the calculation. However, some places I believe an integer is expected:
  • mm-temp-basals.py:102
  • commands.py:189
  • commands.py:359
  • commands.py:1205
  • commands.py:1240
  • commands.py:1467
  • commands.py:1513
• To ensure the same results were gotten in tests, I added sort_keys=True to all the json.dumps calls, e.g. here
• Similarly, all strings are now unicode in Python3, whereas we are working with raw bytes, so I needed to add 'raw_unicode_escape' to the comparison in several tests

[scottleibrand]

I don't see anything here intended to change behavior, or otherwise concerning. If testing looks good, I think this is good to merge.