Correcting or and adding not

Previously, OR filters always returned true (fixes #500).
Convenient factories for logical filters
Doc fixes
Add ol.tilegrid.TileGrid.getTileCoordChildTileRange
Use high resolution tiles in WebGL renderer
Use high resolution tiles in Canvas renderer
Use high resolution tiles in DOM renderer
Store maxZoom in ol.tilegrid.XYZ
Add optimized version of getTileCoordChildTileRange for ol.tilegrid.XYZ
Remove preload from examples that don't need it
Propagate return value
Do not use getView2D in the examples
Add a parser for reading and writing KML.

This adds ol.parser.ogc.KML which can be used to read and write KML documents.
NetworkLinks are retrieved asynchronously.
Current caveats of the implementation are:

* LabelStyle not yet implemented. Missing support in renderers.
* When using shared structures the parser needs to be configured with
  dimension 2.
* We need a better way to disable fill, currently we use opacity as a
  workaround.
* We cannot really roundtrip documents, since some of the info is not
  preserved in the ol structures. But we can write out most of the important
  info.
Merge pull request #509 from twpayne/use-high-resolution-tiles

Use high resolution tiles
move examples/kml to examples/data/kml
Add calculateCenterZoom|Rotation to ol.View2D
Add constrainResolution|Rotation to ol.View2D
Merge pull request #501 from tschaub/logical

Logical filter touch-ups
Add ol.TileCoord.createOrUpdate
Enable ol.TileCoord re-use