Set blocks _layoutOptions to editorOnly: true

This is to prevent the property being written to the JSON files on
preview/publish.
Moved 'tags' property to relevant places

Articles, blocks, and components had been inheriting this.
Added move icon for draggable handle

This affects content objects, articles, blocks and components.
Merge pull request #508 from adaptlearning/tidy-up-issues

Tidy up issues