Nuxeo Birt integration should be support Birt Engine 4.2

from Birt 2.6 to Birt 4.2

Current nuxeo-birt integration module is based on Birt 2.6.1 :

 <dependency>
        <groupId>org.eclipse.birt</groupId>
        <artifactId>report-engine-api</artifactId>
        <version>2.6.1</version>
 </dependency>

We should update to the latest version of birt (4.2) to be able to use report created with the latests versions of Birt Designer.

We probably don't need to make specific work to maintain compatibility with Birt 2.6 : we'll rely on what backward compatibility is provided by Birt itself.

Birt runtime

One of the main change, may be about the BirtFSDeployer since it looks like the Birt Engine bootstrap may have changed.

For Birt 2.6, the custom deployer was based on the Birt ReportViewer sample servlet.
Actually we use birt-runtime-all "home made" jar to embed a ready to run Birt Engine.

Look like things have evolved on Birt, and there are more "off the shelf" runtimes : http://www.eclipse.org/birt/phoenix/deploy/viewerSetup.php