Dashboard models

This PR depends on the django-cms PR
`resource_area` field has the purpose to create custom community URL. Suppose the website URL is http://systers.org, then the custom URL to subcommunity AsianWC, will be http://systers.org/asianwc/.

We might also have subdomains for representing subcommunities - http://asianwc.syster.org/, which looks very neat. But I am not familiar how to implement something like that and what kind of server configuration it requires. Also consider that we want to create subdomains on the fly for each new subcommunity.

In any case `resource_area` is more of a slug. We don't want to have absolute URLs, because the domain name can change. Take a look at [SlugField in Django](https://docs.djangoproject.com/en/dev/ref/models/fields/#slugfield).