nzbget: add devel and test, make conf persistent

Add development release, add test, install configuration file in ```#{HOMEBREW_PREFIX}/etc``` so that it persists after upgrades and removals (was previously installed to the Cellar), use Homebrew's OpenSSL by default, change format of ```make``` commands.
We're moving towards using Homebrew's openssl exclusively, so this can be unconditional, actually.