New modules: imgadm and vmadm (SmartOS Virtualization)

Hi, first time contributor here.

I noticed that there was no module to manage virtual machines with ansible for smartos, and decided to give it a try.

All the implemented bits *appear to* be working as expected. I have reviewed the code as best as I can, and hopefully no glaring mistakes made through that.

Being my first contribution, please do let me know if anything is horribly off. Thank you.