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

bin/gdk

@@ -4,7 +4,14 @@ require 'fileutils'
 def main
   case ARGV.first
   when 'init'
-    system(*%W(git clone -b gdk-cli https://gitlab.com/gitlab-org/gitlab-development-kit.git))
+    if ARGV.count > 2
+      puts "Usage: gdk init [DIR]"
+      return false
+    end
+
+    cmd = %W(git clone -b gdk-cli https://gitlab.com/gitlab-org/gitlab-development-kit.git)
+    cmd << ARGV[1] if ARGV.count == 2
+    system(*cmd)
   else
     $gdk_root = find_root(Dir.pwd)
     if $gdk_root.nil?