Fix indent and spaces
Split ICMP and ICMPv6 types on Firewall Rules

- Remove redundant declaration of $icmptypes and move it to a common
place (filter.inc)
- Add missing ICMP types for v4
- Add ICMPv6 types
- Adjust javascripts to show correct options depending of IP Protocol
- Hide ICMP type selection when protocol is IPv4+v6

It fixes #3389