Function to set default policy

This is no functional change, but reduces code duplication.
Add trap to block everything on failure

If the script fails for some reason, it should not leave everything open
to the world but block everything.
Resolve hostnames before enableing the block policy

After the default policy is in place, DNS may no longer work because it
depends on rules not yet set. An example of this is DNS traffic which
goes through a tunnel which needs some rules to be in place.

The idea here is that the previous configuration hopefully allows these
DNS queries to succeed. If this is not the case there is nothing we can
do anyway.
Remove misleading comment

Git-Dch: ignore
Update changelog for version 1.5