First Commit of Animation

Here it is.

I'm feeling pretty good about the API but the real test will be when someone other than me ports to it or builds their own bot with it. 

If anybody is willing to try this out I will bend over backwards to help them. I need the perspective of someone who is new to it.

I've got some basic documentation over in docs/animation.md but it's not really written well for beginners. Once the API is golden I need to write a wiki page that's more of a tutorial. There is a lot to digest here.

This PR is the culmination of all the discussion in #304 also fixes #362
I could certainly handle most of the normalization back in Animation and just use a getter to grab the last value. The only thing that varies between device types is how the last value is read.

We already have getters for history, last and position. Position is unaware of inverse or offset and the label is not abstract enough to work for all devices (there's no reason we might not animate LED's or other devices in the future). "requestedValue" maybe?