Add .sql.gz to default block list for nginx-drupal

[cdchris12]

This PR adds logic to the nginx-drupal image to automatiaclly block .sql.gz files by default.

Closes #74

[Schnitzel]

doesn't the .*sql already match foobar.sql file?

[cdchris12]

Good catch! I searched for .sql and didn't find it, so I added it as well. I'll update and remove that now.

[tobybellwood]

I'll have a bit of a think about how best to test some of these default rules - I think we can write a testing doc that covers them, it's just where to put it!