Clear cached mousedown/up positions used for distinguishing between
drag and click in feature handler after a click event.

Fixes #856
Add unit test for cleared cache, and adjust existing unit test which
assumed cached position
Remove dangling space in license header.
Give ArcGISCache layer a license header.
Adjust license header of vendorPrefix.js.
Adjust license header of Animation.js.
Adjust license header of WPSClient.js.
Adjust license header of WPSProcess.js.
Merge pull request #873 from marcjansen/dangling-license-space

Remove dangling space in license header.
Tile images should not have an id

When the TileManager adds an image to its cache, it might be a backbuffer
image. Backbuffer images have an id with a '_bb' postfix. Regular images
do not have an id at all. In OpenLayers.Layer.Grid, in
addTileMonitoringHooks, a loadend listener is created for each tile. This
listener checks for tie image id, and will remove it from its parent node.
This will cause images to be removed from the layerDiv if the image comes
from the TileManager's tileCache and was on a backbuffer by the time it was
added to the cache.

Simply removing the image's id before assigning it to a tile resolves the
issue.
Merge pull request #874 from ahocevar/tilemanager-backbuffer-id

Tile images should not have an id. r=@bartvde
the tileQueue is not always cleared, for instance when adding a layer in GeoExplorer and then switching base layers, so make sure we also clear the tileQueue when the visibility of a layer changes
Merge pull request #876 from bartvde/tilemgr-changelayer

the tileQueue is not always cleared, for instance when adding a layer in... (r=@ahocevar)
Subtract page scroll from button position, since clientX/Y is relative to the viewport not page
Merge pull request #877 from finn-no/panzoombar-fix

Fix click on PanZoomBar when page is scrolled (fix #798).
Merge pull request #857 from faegi/featureClickPatch

Clear cached mousedown/up positions used for distinguishing between (fix #856).