Datastructures Restructure

[tomvanmele]

What type of change is this?

• Bug fix in a backwards-compatible manner.
• New feature in a backwards-compatible manner.
• Breaking change: bug fix or new feature that involve incompatible API changes.
• Other (e.g. doc update, configuration, etc)

Checklist

Put an x in the boxes that apply. You can also fill these out after creating the PR. If you're unsure about any of them, don't hesitate to ask. We're here to help! This is simply a reminder of what we are going to look for before merging your code.

• I added a line to the CHANGELOG.md file in the Unreleased section under the most fitting heading (e.g. Added, Changed, Removed).
• I ran all tests on my computer and it's all green (i.e. invoke test).
• I ran lint on my computer and there are no errors (i.e. invoke lint).
• I added new functions/classes and made them available on a second-level import, e.g. compas.datastructures.Mesh.
• I have added tests that prove my fix is effective or that my feature works.
• I have added necessary documentation (if appropriate)

[tomvanmele]

by using the "IPY guard" where necessary, i would like to add all data structure algorithms to the corresponding classes. this would simplify many things

• users doesn't need to import every single algorithm they want to use
• easier to document
• "pulling up to 2nd level" requires less maintenance
• class becomes the public API of the corresponding package

one potential advantage is also that all algorithms and their dependencies don't have to be pre-loaded at the 2nd level. however, this requires the imports at the class level to be integrated at the method level. otherwise everything is again automatically loaded when the class is loaded...

opinions?

[gonzalocasas]

LGTM!