Opify static methods

[gselzer]

This WIP PR intends to "opify" the static functionality within the project, and is divided into two subtasks:

1. Declare all op-like algorithms as Ops using the SciJava Ops Indexer
2. Migrate all Ops operating on Meshes from scijava-ops-image to here.

I've additionally filed issues for, or just outright added, functionality that was declared to work in scijava-ops-image/ImageJ Ops but was not functional:

• Added Meshes.boundingBoxMesh that creates a bounding box Mesh from another Mesh.
• Filed Add smallest enclosing box algorithm #8 and Add boxivity algorithm #9

Points of discussion:

• I find the geom.mainElongation and geom.medianElongation Ops to have confusing names, as I could find no literature that named these properties. My understanding is that geom.mainElongation measures the elongation of a cross-section ellipse, where the section is perpendicular to the two larger semi-axes, while geom.medianElongation does the same but with the two smaller semi-axes. @tibuch is this correct? At a minimum I want to document this, but better would be to come up with better names so we can alias the Op.

[tibuch]

Absolutely agree with the confusing naming. Maybe Major- and MinorElongation would be better. Or simply return an ElongationVector similar to EigenValues.

I would definitely drop MedianElongation because there is no median involved.

[hinerm]

@tinevez In this PR we are discussing the minimum Java version to index libraries with Ops. I'm wondering if there is a need to keep imglib2-mesh at Java 8, or if going to Java 11 is an option?

[tinevez]

Hello @hinerm
The next release must be able to be shipped and used within Fiji without modifications.
When Fiji is shipped with Java > 8, then we can do the same here.

[gselzer]

Hi @tinevez, I've written this PR to require Java 11+ compilers (to enable Ops annotation processing), but Java 8 code. It should work just fine in a Java 8 Fiji! Please let me know if you have any questions or concerns with this.

[tinevez]

Thanks for the clarification! The difference between compile time requirements and execution time requirements escaped me.
It's all good on my side then.