Refactor heat.py into a subpackage

[jzuhone]

Description

heat.py currently contains all of the classes which model heating inputs. Currently, this file is quite bloated, containing all currently used classes, as well as some which are no longer used.

This PR refactors this structure, while leaving the API intact, by changing heat.py into a heat subpackage. The files under heat are now:

• base.py: base heating classes
• generic.py: generic heating classes (this could be merged into the one above potentially)
• solar.py: all of the solar heating classes
• earth.py: the earthshine in the ACIS radiator FOV code
• electronics.py: heating from electronics boxes

I also put deprecated classes into a new file, deprecated.py, under the component subpackage.

This PR also:

• Removes the DpaSolarHeat copy of the SolarHeatHrc class
• Removes from future import print_function call at the top of heat.py

Interface impacts

Since this is just code reorganization under the hood, but all imports from the xija API should be the same, there should be no interface impacts.

Testing

Unit tests

• [x] Mac

Independent check of unit tests by @taldcroft

• [x] Mac

Functional tests

xija_gui_fit and acis_thermal_check tests pass.

[taldcroft]

@jzuhone - I added a test we should have had long ago which runs every model in chandra_models. With this test in place I'm good with this PR once you do functional tests, without having really checked the refactor details.

[taldcroft]

@jzuhone - this is just waiting for those quick functional tests. Let's get this in then I can do the black format PR for xija. :smile:

[jzuhone]

Hi @taldcroft I ran the functional tests and all looks good.