Adding WordPress import file

Adding a WordPress import file, which allows one to define which plugins..., amongst other things, should be installed and optionally activated after WordPress is installed. Note that everything is commented out by default, so out of the box, this doesn't change any functionality. It does however make it easier and more intuitive for developers to add plugins, mu-plugins, themes, etc. to their WordPress environments when Vagrant is first fired up. Related: see #108