Use CoreData to store servers you connect to.

The password you use to connect is in the clear. My understanding is that
CoreData entities are stored in sqlite, so I'd like to avoid doing this,
but I haven't had time to read up on best practices.

Some of the annoying problems I encountered as part of this commit were

* adding CoreData to an existing project
  -- Mainly the issue I had was I wasn't referencing the correct
     #{Model}.momd file in my bundle, and I wasn't using the
     right entity when I was. Easily fixed
* Referencing my app delegate from other classes
  -- this seems likely to cause circular #import chains because my
     app delegates tend to do too much. Even if they don't, they
     need to import __SOMETHING__, which will import several other
     headers, one of these descending headers will of course
     need to import the app delegate. Either way, using some
     forward declarations of @class fixed all of my warnings.
* default values for text fields
  -- it would be very nice to have some classes that encapsulate
     the textfield and have a default value, so I can ask for
     their value and not care what the actual value is.