[spp] Need more simple usecases for spp_vf and spp_mirror

[Yasufumi Ogawa <usufumu@gmail.com>]

Hi Hideyuki and team,

I think usecases, "Simple SSH Login" for spp_vf and "Mirroring packet 
from a VM" for spp_mirror, are too complex to try at the first time for 
beginners.

"Simple SSH Login" is simple in a mean because it is simply logging in 
with ssh, but no need to prepare two VMs and twelve threads. I think it 
is OK if this usecase is an advanced tutorial, but not appropriate for 
the first usecase. I think it is better to explain each of components 
step by step.

I think the same for spp_mirror. Spp_mirror is for simply duplicating 
incoming packets, so no need to explain with spp_vf and no need to use 
three VMs.

I suppose you thought it is better to explain with more practical 
usecases, and I agree with your idea. However, we need to explain 
simpler usecases before them. I hope you agree with.

Thanks,
Yasufumi