Add support for AIX Platform

[alexmanly]

Extend the reach of this cookbook by also supporting managing LVMs in the AIX platform.

[juliandunn]

A community member is working on some stuff over here: chef-cookbooks/aix#15

[willdearborn]

Hello, not to drag up an old issue, but:

I was over at the aix cookbook site. Looks like there is a volume_group provider there, but there was discussion that it might not be the best place, and that perhaps IBM was working on it. At the speed of IBM may not be very fast.

I forked this repo, and started working on AIX functionality (volume groups for now), what is the appetite for seeing a PR for that here when it's complete?

https://github.com/willdearborn/lvm/tree/wd/aix