Better mousewheel/touchpad behavior for zooming

The navigation control gets better defaults, and the MouseWheel handler
gets a new maxDelta option, which can be used to avoid huge zoom level
jumps on heavy wheel/pad movements.
Use translate3d and translate where available.
Turn on GPU support for all children of the layerContainerDiv

This seems to remove all kinds of flicker and jumpiness, and to me it feels
also like it makes panning on slow mobile devices smoother.
Adding docs, removing console.log
No backbuffer removal delay needed with 3d enabled
Giving the last tile time to render

The loadend event of an image is fired before the image is rendered. For
standard 256x256 tiles, this does not matter. But for singleTile layers on
large screens, rendering time needs to be considered. So we add a delay
that depends on the tile size. TODO: make the denominator configurable.
No magic for loadend delay

This change reintroduces the removeBackBufferDelay, and documents exactly
what it does and when it may be useful.
No closure, to make testing easier
Updating and adding tests
GPU needs to be turned on for all elements we move
Adding transforms to turn on GPU
Own applyTransform method is no longer needed
Going one element up with GPU support, adding it to mobile css also
Do not set translate3d on svg children

In current Webkit browsers, having translate3d on svg child elements
causes the positioning from the layer not to be inherited by the vector
layer content.
Only use 3d transforms when stylesheet has transform on layerContainerDiv

This allows users to control whether 3d acceleration should be used or not:
Just like with plain web pages, having a stylesheet that sets a transform
on the map's layerContainerDiv will make OpenLayers use translate3d and
scale3d. When no such transform is set in the stylesheet, style.left and
style.top will be used, except for e.g. pinch zoom, where scaling is
needed.
3d transforms in svg content are bad in other browsers as well
Revert "No backbuffer removal delay needed with 3d enabled"

This reverts commit 7e8271525ed52288092a135b1c65eed4849c8e49.
Put backbuffer below all layers, except when panning
Better way to get GPU support, and avoid flicker

These declarations were suggested on
http://blog.teamtreehouse.com/increase-your-sites-performance-with-hardware-accelerated-css
Adding animated zooming