Userlocation update

That PR brings a few things:
- a new user location image
- all densities support for a sharper drawing
- sort of overlays to draw paths, then markers, then user location

Notes:
- it s a proposal, the image can actually be change
- i put the psd in the root folder, where should i put it?

![screen shot 2014-03-24 at 16 04 39](https://f.cloud.github.com/assets/655344/2500809/4b12400e-b366-11e3-8af0-4cab7715d7cf.png)