Restore MAPL Python2 import behavior

[mathomp4]

Description

As pointed out by @amdasilva, the MAPL Python interface inadvertently lost its Python2 behavior in re __init__.py. This restores that by adding back the from .foo import * lines.

Moreover, testing by @patricia-nasa found more bugs in the MAPL python code. Essentially, a lot of it was not Python3. Now it is.

Related Issue

Motivation and Context

Restores our MAPL Python behavior to pre-Python3.

How Has This Been Tested?

I'll probably ask @patricia-nasa to do some tests for me.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Trivial change (affects only documentation or cleanup)

Checklist:

• I have tested this change with a run of GEOSgcm (if non-trivial)
• I have added one of the required labels (0 diff, 0 diff trivial, 0 diff structural, non 0-diff)
• I have updated the CHANGELOG.md accordingly following the style of Keep a Changelog