added 'router-list', 'subnet-list' subcommands.

Hi,

I added two commands which list up these information.

* subnets
* routers

<pre>
% knife hp router list
Name              ID                                    Tenant          Admin State UP  Status
jedipunkz-router  38edb13e-0e04-469f-92b5-c2b424fbe968  10626936184240  true            ACTIVE
% knife hp subnet list
Name              ID                                    Tenant          Network ID                            Gateway IP  CIDR Addr
jedipunkz-subnet  50bf401a-a8fe-444d-b231-611c053a0bd5  10626936184240  62ebc3c2-be6c-483b-ae3b-cd0cb24edf9d  10.0.0.1    10.0.0.0/24
</pre>

Thanks.