Clarify keyboard events and focus in docs
Use projection option instead of reprojectTo

The projection option for vector file sources currently has no good meaning.  The reprojectTo option is used to set the projection for cached features.  This change makes it so the projection option is used for this purpose.  The getProjection method (not currently exported) can then be used to get the cached feature projection.

This also removes the default of 'EPSG:3857' for vector file sources.  If a projection is not configured, features will not be transformed.
Rename render/featuresoverlay files to featureoverlay
Rename ol.render.FeaturesOverlay to ol.FeatureOverlay
goog.require in alphabetical order
Variable renaming in examples
Use featureOverlay in select interaction
Change olx.render.FeaturesOverlayOptions to olx.FeatureOverlayOptions
Fix minor typo in vector-layer example
Close the polygon created by ol.render.Box
Simplify code in ol.render.Box#createGeometry_
Fix typo in tests
Fix closing tag in tests
Add ol.xml.load
Use ol.xml.load in ol.format.XML
Use ol.xml.load in ol.format.KML
Use ol.xml.load in ol.source.VectorFile
Add ol.xml.isDocument
Use ol.xml.isDocument in ol.format.XML
Use ol.xml.isDocument in ol.format.KML