Add scripts for performing common tasks to make it easier to contribute

It's easy to contribute when everything is right there, sitting in front of you, with semantic names. Want to boot up the server? Run `script/server`. Want to install the dependencies of the project? No problem. Just run `script/bootstrap`.

These kinds of scripts make it easier to contribute to a site, both for external contributors (like me!) and for internal contributors, like you.
On a brand new clone, you need to create this directory first. A plugin is reaching into it before it's been created.