Make GDK config ruby object the SSOT

This changes ensures all configuration sources from the config object.

The order of precedence is now:

• gdk.yml
• loose files: port, hostname, etc.
• lib/gdk/config.rb

This change should not interrupt any users, because it should keep using the same values if you're using the the loose files.

Closes #413 (closed)

HTTPS locally

With this change I was able to run HTTPS locally. Steps to set up:

• Create a new loopback network device:

  # macOS
  sudo ifconfig lo1 alias 127.1.1.1
  # linux
  sudo ifconfig lo:1 127.1.1.1

• Add a host to /etc/hosts:

  echo '127.1.1.1 gdk.test' >> /etc/hosts

• Create certificate with mkcert:

  mkcert gdk.test 127.1.1.1

• Use the following gdk.yml:

  ---
  hostname: gdk.test
  nginx:
    enabled: true
    http:
      enabled: true
    ssl:
      certificate: gdk.test+1.pem
      key: gdk.test+1-key.pem
  port: 443
  https:
    enabled: true

• Run gdk reconfigure

• 💥

Future

This change allows us to slowly move away from Makefile targets and implement one-by-one with Ruby in Rakefile.