Create first listing

This does a few things:

User can now create a first listing from their dashboard.  This is eventually meant to be a feature only for new users, and it will be the first thing they see.  This seems suited to the next iteration though.  

The "Admin" controller namespace still exists (the name is likely to change to "host") and the technique for authorization is different now.  Authorization is now based on user-identifying information instead of checking if the user's role is "admin".

There is also some additional clean up type things that didn't seem to justify their own branch (I could very well be wrong on this, but in this case I just bundled them in).