Enable hover rotation on position icons

Here's a preview of the feature included in this pull request.

![bloggif_547d8f0db3890](https://cloud.githubusercontent.com/assets/895039/5260811/f37bb85a-7a77-11e4-8793-136487c93f07.gif)

I would just like to raise how similar the new iconography is to each other and it feels like it relies on colour a lot more than the old choices [did].

For one of the main interactions of the app I would argue distinct icons for each action would heavily boost usability.

Thoughts?