zebra: show routes in a specified VRF or all VRFs

zebra: show routes in a specified VRF or all VRFs

The present "show ip[v6] [m]route [xxx]" and "show ip rpf [xxx]"
commands now show routes only in the default VRF.

A new option is introduced to show routes in a specified VRF:
    show ip[v6] [m]route [xxx] vrf N
    show ip rpf [xxx] vrf N

and a new option is used to show routes through all VRFs:
    show ip[v6] [m]route [xxx] vrf all
    show ip rpf [xxx] vrf all

Signed-off-by: Feng Lu <lu.feng@6wind.com>
Reviewed-by: Alain Ritoux <alain.ritoux@6wind.com>
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Acked-by: Vincent JARDIN <vincent.jardin@6wind.com>
[DL: conflicts resolved]
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
Conflicts:
	zebra/zebra_vty.c

Conflicts:
	nhrpd/nhrp_interface.c
	zebra/zebra_rib.c
	zebra/zebra_rnh_null.c
	zebra/zebra_vty.c