Feature: Scrollbar and metrics

[RoryPTB]

Major Changes

• GDC results now have a scroll bar and a scroll-to-top button that appears after scrolling down sufficiently.
• Users can now order GDC results by latest or oldest creation dates and filter results by datasets with a topic.
  The downloaded bytes section of the topic monitoring page now automatically scales from bytes to KB, MB, and GB, and the associated title is updated accordingly.

Minor Changes

• The tables of pending and active topics in the Subscribe page now have a scroll bar.
• Fixed the bug where topics could not be removed from the Explore page.