ffa516d  Fixes #3134, added bulk tracking feature and bulk request API method.

Notes:
  * Modified php tracker lib so bulk tracking can be used (via enableBulkTracking & doBulkTrack methods).
  * Modified DocumentationGenerator.php to generate example URLs using Piwik_Url instead of creating it by hand.
  * Fixed bug in XML DataTable renderer where row values weren't escaped when the row has one value and no columns.