Dirty attribute

[petrasvestartas]

Development of new features:

• is_dirty attribute of element that affects neighbor elements too
• high-light dirty elements for viewer
• element has a driver property that also affect graph edge direction

Attribute is_dirty is set when the interaction is computed on the outwards neighbours:

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)

[petrasvestartas]

This file will be used to draft a simple model where one element is changed by another to trigger "is_dirty" attribute for current and neighbours_out elements.

Later this example will be changed to a test file.