File upload improvements

* Added plupload library for file browser
* Changes on OperationEngineController.java to support plupload
* Include plupload resources and dependencies
File upload improvments

* Allow use plupload as file browser option
* Some additional options for plupload option: `maxFileSize`, `chunkSize` and `extensionFilter`

Default upload manager it's the old approach, to activate the new manager, override the option with `fileBrowser.uploadMethod=PLUPLOAD`.
Merge pull request #37 from alediator/plupload_include

File upload improvements