treewide: consolidate {IPv4,IPv6,MAC} {address,gateway} spellings

 - Turn IPv4-Address into IPv4 address
 - Turn IPv4-Gateway into IPv4 gateway
 - Turn IPv6-Address into IPv6 address
 - Turn IPv6-Gateway into IPv6 gateway
 - Turn MAC-Address into MAC address

Also remove related duplicate translation entries.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>