Improve setup for Gitpod

[geropl]

This removes foreman, and uses Gitpod tasks instead:

• init pulls and builds dependencies, db setup
• two commands, in terminals next to each other, started after init finished successfully (using poor mans file lock):
  • bundle exec rails s -b 0.0.0.0
  • bundle exec hyperstack-hotloader -p 25222 -d app/hyperstack/
• once puma started, open port 3000 in the preview