renamed install-security-updates => turnkey-install-security-updates

rational: so that autocomplete works as suggested by John Carver
Leverage dpkg-reconfigure to regenerate SSH keys
renamed:    install-security-updates -> turnkey-install-security-updates

That way users can use turnkey-* shell autocompletion to discover the
install-security-updates script
Merge branch 'master' of github.com:turnkeylinux/inithooks