Blender Git Loki

Fix T58502: scopes don't work in the image editor

There were two problems:
1. The scopes were only updated when the "Scopes" category is active,
but this category has been removed in Blender 2.8.
2. The scopes moved from the TOOLS to the UI region.
However the update-code still searched for the "Scopes" category
in the TOOLS region.

Both problems are fixed with this commit:
1. Scopes have there own category again.
2. The update code is in the correct draw function now.

Reviewers: brecht

Differential Revision: https://developer.blender.org/D4245