Rename hlp to common in hlp package

[tizianocitro]

All Submissions

• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

Description

• Renamed hlp.py to common.py.

Checklist

• Does your submission pass all tests? (use make test)
• Have you written tests to cover all your changes? If not, provide a reason.
• Have you lint your code locally before submission? (use make lint)
• Have you type checked your code locally before submission? (use make typecheck)
• Have you added an explanation of what your changes are and why you'd like us to include them?