More than one complaint about how it looked before.

per: #28

Fix docker dependency to Pg::SQL::PrettyPrinter

See merge request !23

Dockerfile seems to be missing dependency Pg::SQL::PrettyPrinter. Adding it to the install seems to make it work as expected.

Per suggestion from Ugo Bellavance

Design updates for queries and source

See merge request !22

Keep horizontal scroll bars visible in the plan.

See merge request !20

Cursors cause bug in Pg15

This is so that I will find things to work on for next improvements in
the site.

1. Help page is updated to newest functionality
2. you can now copy plans to clipboard (as requested by Eugen Konkov)
3. Rows removed by filters are displayed in plan view
4. URLs with #elements will now automatically open/select requested
   element (including: source, text, stats, specific lines) - also
   requested by Eugen Konkov.
5. Made explain.js a bit smarted about hiding/showing content when user
   clicks on tabs
6. Updated dependency to newest Pg::Explain
7. Fixed display of returned rows for multi-loop or multi-worker nodes