Implement GPX parser (read/write).

Implement a parser for GPX which supports read and write.
address review by @fredj
make feature info work on touch devices for gpx example see #727
Fix XML serialize and xml_eql in IE9

Use the xml property instead in IE for serializing XML.
The xml_eql tests were failing in IE9 on a difference between null and an
empty string for namespaceURI of attributes, this difference is not
relevant to our testing so make sure we ignore.
Static read and write functions on WKT parser

Use a singleton to implement static read and write methods on ol.parser.WKT.
Add parser.jsdoc file for docs on parser options.

Pointer by @ahocevar in #735
Merge pull request #736 from bartvde/jsdoc2

Add parser.jsdoc file for docs on parser options (p=@ahocevar, r=@bartvde)
FeatureId support in GML (r/w) and KML (w)

Now that we have FeatureId support (see #733), we can add this back to the
GML parsers (v2 and v3). Also add write support for FeatureId in KML, read
support was already added by @fredj
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
Move squarifiedRatio into private static function
Move makeMBR into private static function
Make minWidth and maxWidth private member variables
Move more functions into private methods
Move search and searchReturningObject into methods
Move remove into method
Move insert into method
Clean up some comments
Sort methods alphabetically
Add ol.extent.empty