Rename perfplat.dev to full dev domain

Maintaining 2 domain names in development is a pain, so we're just
going to use the full one.
Increase server_names_hash_bucket_size everywhere

Now that we have super long domain names in development, we're running
into an error with Nginx starting:

    2014/05/02 15:30:38 [emerg] 13185#0: could not build the server_names_hash, you should increase server_names_hash_bucket_size: 64

@robyoung and I can't imagine that this will cause any massive impact
on the machines that don't currently receive it (backend boxes etc),
so increase it across the board.
Merge pull request #384 from alphagov/perfplat-dev-development-domain

Rename perfplat.dev to full dev domain