Add 'gdk' command wrapper and gem

Combine make and ./run into gdk. Can be invoked as gdk, e.g. gdk run db.

This does not remove make and ./run, it just adds an integrated wrapper.

Installation become:

gem install gitlab-development-kit
gdk init # clones repo
cd gitlab-development-kit
gdk install gitlab_repo=https://bla

HELP

@@ -5,7 +5,7 @@
 ./gdk run app        # Start GitLab, need './run db'
 ./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 update                                # Pull application changes from Git
+./gdk reconfigure                           # Delete and regenerate all config files created by GDK
 # Development admin account: root / 5iveL!fe