Resolve "Unify `gdk help` and `gdk --help`"

What does this Merge Request do?

Unify the output of gdk help and gdk --help.

$ gdk help


           [38;5;88m`                        `
          :s:                      :s:
         `oso`                    `oso.
         +sss+                    +sss+
        :sssss:                  -sssss:
       `ossssso`                `ossssso`
       +sssssss+                +sssssss+
      -ooooooooo-++++++++++++++-ooooooooo-
     [38;5;208m`:/[38;5;202m+++++++++[38;5;88mosssssssssssso[38;5;202m+++++++++[38;5;208m/:`
     -///[38;5;202m+++++++++[38;5;88mssssssssssss[38;5;202m+++++++++[38;5;208m///-
    .//////[38;5;202m+++++++[38;5;88mosssssssssso[38;5;202m+++++++[38;5;208m//////.
    :///////[38;5;202m+++++++[38;5;88mosssssssso[38;5;202m+++++++[38;5;208m///////:
     .:///////[38;5;202m++++++[38;5;88mssssssss[38;5;202m++++++[38;5;208m///////:.`
       `-://///[38;5;202m+++++[38;5;88mosssssso[38;5;202m+++++[38;5;208m/////:-`
          `-:////[38;5;202m++++[38;5;88mosssso[38;5;202m++++[38;5;208m////:-`
             .-:///[38;5;202m++[38;5;88mosssso[38;5;202m++[38;5;208m///:-.
               `.://[38;5;202m++[38;5;88mosso[38;5;202m++[38;5;208m//:.`
                  `-:/[38;5;202m+[38;5;88moo[38;5;202m+[38;5;208m/:-`
                     `-++-`[0m

  
# GitLab Development Kit

Usage:

gdk start                                 # Start everything
gdk start redis postgresql                # Start specific services
gdk stop                                  # Stop all services and unload Runit
gdk stop redis postgresql                 # Stop specific service
gdk status                                # See status of all services
gdk restart                               # Restart everything
gdk restart redis postgresql              # Restart specific services

gdk tail                                  # Tail all logs
gdk tail redis postgresql                 # Tail specific logs

gdk thin                                  # Run rails web server with thin in foreground

gdk init                                  # Initialize GDK
gdk install gitlab_repo=https://my-fork   # Install everything
gdk update                                # Pull application changes from Git
gdk reconfigure                           # Delete and regenerate all config files created by GDK

gdk psql -d gitlabhq_development          # Postgres console
gdk redis-cli                             # Redis console

gdk config get postgresql.port            # Get configuration values
gdk diff-config                           # Print difference between current and new configuration values
gdk doctor                                # Run diagnostics on GDK

# Development admin account: root / 5iveL!fe

For more information about GitLab development see
https://docs.gitlab.com/ce/development/README.html.

Merge Request checklist

• [-] Tests added for new functionality. If not, please raise Issue to follow-up.
• This change is backward compatible. If not, please include steps to communicate to our users.
• [-] Documentation added/updated, if needed.
• [-] gdk doctor test added, if needed.

Closes #696 (closed)