Allow setting armature axis manually

[TackYs]

@niftools/blender-niftools-addon-reviewer

Overview

When importing armatures, axis are currently set automatically by the guess_orientation function in nif_import/armature/init.py

# use heuristics to determine a suitable orientation 
forward, up = self.guess_orientation(n_armature) 
# pass them to the matrix utility 
math.set_bone_orientation(forward, up)

Some times it would be valuable to be able to set these manually, example is if you have a rigged armature in the scene with a specific orientation and want to import another armature with matching orientation.

Detailed Description

[List of functional updates]

Fixes Known Issues

[Ordered list of issues fixed by this PR]

Documentation

[Overview of updates to documentation]
I put in a block in the draw() call for setting axis if guess orientation is checked, that together with the operator descriptions is hopefully clear enough?

Testing

[Overview of testing required to ensure functionality is correctly implemented]
Import nif skeleton with guess armature checked, then import the same armature again with different orientations checked.
Compare bone rolls.

Manual

[Set of steps to manually verify updates are working correctly]

Automated

[List of tests run, updated or added to avoid future regressions]

Additional Information

[Anything else you deem relevant]

[TackYs]

Maybe the checkbox option should be labeled "detect armature orientation" instead of "guess armature orientation"

[HENDRIX-ZT2]

Maybe the checkbox option should be labeled "detect armature orientation" instead of "guess armature orientation"

Or Override Axis Armature Orientation? I feel like if you have this set manual orientation feature, and by default the manual setting would be off, we should name the toggle accordingly so you know what happens when you check it -> ie. you need to set the axes manually in the widget that appears.

[TackYs]

I agree, changing it to an Override option with default False makes much more sense!
Will update PR.

My internet is out since yesterday so ill commit when ( if? D: ) it comes back

[neomonkeus]

Good to merge?

[HENDRIX-ZT2]

@TackYs @neomonkeus should try to implement orientation_helper instead of hardcoding the axes

[TackYs]

Had a go at using orientation_helper as per Hendrix suggestion
As a result it was possible to remove most of the extra properties defined in NifImportOperator in the first commits, seem to work well.

Split the override settings into a separate panel - optional, can go back to one panel. Not really sure what feels best.

[HENDRIX-ZT2]

Great!

[HENDRIX-ZT2]

There's a utility for this:
bpy_extras.io_utils.orientation_helper(axis_forward='Y', axis_up='Z')
https://docs.blender.org/api/current/bpy_extras.io_utils.html

[HENDRIX-ZT2]

Have you looked into this? Should make the code more elegant :)

[HENDRIX-ZT2]

perhaps don't draw the axes at all?
also comment format for pep (2 spaces before inline #, 1 after)