Resolve "Make file browser hidden by default for mobile screens" and improve layout in small screens too

What does this MR do?

1. Makes the file tree load closed if no setting is stored in localStorage
2. Improves the layout in small and medium screens.

Demo

Kapture_2018-10-10_at_18.14.09

What are the relevant issue numbers?

Closes #52361 (closed)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides

Closes #52361 (closed)