Allow manual invokation of the IP suggestion logic.

Add the ability to manually request a new IP for a host.

This is useful if the IP that's previously picked up from DHCP isn't what's needed.

![screen shot 2014-04-11 at 10 02 07](https://cloud.githubusercontent.com/assets/98526/2677813/04359956-c158-11e3-90a5-9ad4c23eff96.png)