Replace import dialog using jQueryUpload

The current file upload widget relies on RichFaces.

This implementation has some drawbacks :

• it relies on JSF / Seam
• it maintains access to Seam conversation : this can create lock timeouts in Seam
• upload in done in the context of a Tx
• upload progress is managed server side
• several client/server round trips
• progress is wrong when nuxeo is behind a buffering reverse proxy like nginx

These problems are known for a long time, but it becomes worst :

• when using big files
• when using nginx

The idea is to align on the way the import is currently done via Drag&Drop :

• use Automation Batch API for upload
• run an Operation to do the import

A quick prototype for done for 5.6 :

https://github.com/tiry/nuxeo-jqueryfileupload-integration