Merge projection view module

* view module contains an instance of projection now.
* needed for further support for multiple map projection support in future.
You need some unit to measure tiles so you can do things like calculate how many tiles wide/high the viewport should be for a given zoom level in standard web mercator view. It doesn't have to be "pixels", but it's as good as anything else (and the long-time standard, so I think it's clearer than using something else). With retina/high-density displaces, it's more an abstract unit now than an actual pixel, but that's a problem across all app/web development these days anyway, so not unique here...