Custom landing pages

Ability to create custom landing pages for tenants.

When a user goes to a tenant that has a custom landing page this will be shown instead of the default landing page. nginx checks if a file is present in the `custom` directory that has the name `host.html` (e.g. `thefold.oaeproject.org.html`) and serves it if there is one. If the file isn't found nginx falls back to serving the default landing page.

Inside of the `custom` folder there are a CSS and JS folder, similar to what `ui` has.

This PR also includes the custom landing page for the Fold:

![screen shot 2014-02-11 at 09 40 55](https://f.cloud.github.com/assets/218391/2135540/a5792c78-9300-11e3-9f87-994ef000001f.png)