Static read and write functions on WKT parser

Use a singleton to implement static read and write methods on ol.parser.WKT.
Allow user to stop map at the end of a drag

If the time between the last move and now is longer than the configured delay, this means that the user stopped panning before releasing the map.
Style for attribution control
Merge pull request #729 from bartvde/wktsingleton

static read and write methods on ol.parser.WKT (r=@ahocevar)
Merge pull request #738 from tschaub/allow-stop

Allow user to stop map at the end of a drag
Simplify style
Merge pull request #739 from tschaub/attribution-style

Style for attribution control
Change ol.Object event name syntax

'changed' to 'change' and '<attribute>_changed' to 'change:<attribute>'.