SBX utils: ensure correct photometric setting for TIFs and allow extracting single plane

[ethanbb]

Description

This PR includes two changes:

• A bugfix for the condition when a 3D SBX with 3 or 4 planes is converted to TIF. By default, tifffile assumes the 4th dimension is the color channel, so it is necessary to set photometric to MINISBLACK to avoid each plane being 3-dimensional.
• An added feature, the plane argument to SBX loading/conversion functions, which allows extraction of a single plane without keeping the singleton dimension. This is useful when opting to process each plane of a volumetric dataset individually.

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

Has your PR been tested?

If you're fixing a bug or introducing a new feature it is recommended you run the tests by typing

Yes, caimanmanager test passes and new tests have been added for both of these changes.

[pgunn]

Looks good. Thanks!