#1 Theme tweaks

Fixes #1 

__Note:__ There is one thing that I wasn't 100% sure of one the tweaks I did. I decided to use the default org listing snippet... but that includes a image in it. However since datagm doesn't have any images assigned to orgs yet so I decided to hide the org images on the homepage. It would look a lot better again if it did have images...

So maybe we decide to just not hide the images anyways. Here's the offending line if you want to do this yourself: https://github.com/okfn/ckanext-datagm/blob/1-theme-tweaks/ckanext/datagm/fanstatic_library/styles/datagm.css#L37