src: Wrap netfilter hooks around human readable strings

src: Wrap netfilter hooks around human readable strings

This allows to use unique, human readable, hook names for the command
line and let the user being unaware of the complex netfilter's hook
names and there difference depending on the netfilter family.

So:
add chain foo bar { type route hook NF_INET_LOCAL_IN 0; }

becomes:
add chain foo bar { type route hook input 0; }

It also fixes then the difference in hook values between families.
I.e. ARP family has different values for input, forward and output
compared to IPv4, IPv6 or bridge.

Signed-off-by: Tomasz Bursztyka <tomasz.bursztyka@linux.intel.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>