dnscrypt: add user selectable/manual proxy input.

This adds the ability to pick among the current dnscrypt resolvers.

All that needs to be done to update the list of resolvers is to replace it with the latest version in rom/etc/etc.
At compile time the dnscrypt resolvers in basic-network.asp are populated from the dnscrypt csv file found in rom/rom/etc.

This update also allows a 'Manual Entry' of a DNSCrypt resolvers.
dnscrypt is updated to 1.4.0