Move focus_ position update into handleMapBrowserEvent

Otherwise, the position is only updated on keyboard or mouse wheel events.
Follow-up improvements for #897

* Interaction is no goog.Disposable any more.
* Permanent cleanup during selection instead of disposeInternal.
* Moved selectionLayers creation outside feature loop.
* Maintain selectedFeatures and unselectedFeatures only for
  layers that have a setRenderIntent method.
ol.Attribution is a single-arg constructor
Adapt sources to new signature for ol.Attribution
Adapt examples to new signature for ol.Attribution
Improve documentation for animation-related stuff

The animation-related code is missing sufficient detail to make it
usable without digging in to the code.  This adds some additional
detail to the ol.animation namespace, the related options, and makes
note of the existance of ol.animation in the documentation of
ol.Map.addPreRenderFunction(s).
remove trailing whitespace to make the linter happy.
Use ol.Coordinate instead of ol.geom.Vertex
Rename ol.geom.VertexArray to ol.CoordinateArray
Add missing provide and require for ol.geom
Remove map from control options
Don't export ol.control.Control.prototype.setMap
instanceof check to avoid ducktyping
Do not delete from oldFeatureMap
Add extra requires (see #958)
Merge pull request #950 from pagameba/doc-animations

Improve documentation for animation-related stuff.
Update ZoomSlider example in docs
Call addControl instead of passing map to control
Call setMap instead of passing map to control
Remove handleMapPostrender extension point