Feature/viewer-context-detection

[ZacZhangzhuo]

What type of change is this?

• Added viewerinstance in compas.scene.Scene to support viewers context detection.
• Some import sorting.

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 have added necessary documentation (if appropriate)

In the viewer, checks can be run like:

from compas.scene.context import _detect_current_context
from compas_viewer import Viewer

viewer = Viewer()
print(_detect_current_context())

This PR is associtaed to compas-dev/compas_viewer#12 @tomvanmele @Licini

[Licini]

@ZacZhangzhuo linter error

[ZacZhangzhuo]

This one should be great @Licini

[tomvanmele]

there are some superfluous spaces here

[ZacZhangzhuo]

done