Assembly Nuxeo servers with an xml description file

Add a serverSet definition in order to describe servers to build instead of only one.
Prototype :
<packaging>
<serverSet id="nuxeo-mono">
<includes>
<artifacts group="org.nuxeo.*" category="runtime,core,search,web" includeDependencies="true"/>
</includes>
<excludes>
<artifact group="org.nuxeo.common" />
<artifact name="nuxeo-runtime-jboss-extensions" />
</excludes>
<assembly type="directory" name="nuxeo.ear">
<output pattern="nuxeo-platform-audit-facade" unpack="true" directory="system" />
<output pattern="nuxeo-platform-placeful-facade" unpack="true" directory="system" />
<output pattern="nuxeo-platform-search-compass-plugin" unpack="true" directory="system" />
<output pattern="nuxeo-*" unpack="false" directory="system" />
<output pattern="*" unpack="false" directory="lib" />

<!-- resources downloaded from artifacts -->
<resources output="/" sourceArtifact="nuxeo-platform-ear:resources-core" />
<resources output="/" sourceArtifact="nuxeo-platform-ear:resources-search" />
<resources output="/" sourceArtifact="nuxeo-platform-ear:resources-web" />
<resources output="/" sourceArtifact="nuxeo-platform-ear:resources" />
<!-- local resources overriding default ones from artifacts downloaded -->
<resources output="/" sourceDirectory="src/main/resources" />
</assembly>
<preprocessing>true</preprocessing>
</serverSet>