[bug 931105] Truncate description on dashboard

The dashboard shows the data form ES, so the truncated_description property is the one from the ResponseMappingType.

This causes some minor confusion in that there is a truncated_description property on Response that truncates at a different length and is primarily used by the admin since it's in the `__unicode__` method.

That's the only problem with this that I can see. I'm game for other possibilities. Maybe renaming "truncated_description" in ResponseMappingType to "summary" or something like that?

r?