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

bootstrap

 #!/bin/sh
-cat > gdk <<EOF
+gdk_path=$(pwd)/gdk
+printf "Creating executable: ${gdk_path} ... "
+
+cat > ${gdk_path} <<EOF
 #!/bin/sh
 export GDK_ROOT=$(pwd)
 export GDK_INVOKED=\$0
 exec /usr/bin/env ruby \$GDK_ROOT/gdk.rb "\$@"
 EOF
-chmod +x gdk
-
-exec ./gdk install
+chmod +x ${gdk_path}
+echo done
+echo
+./gdk help