webadmin: gwt-common project maven configuration
webadmin: gwt-common project maven configuration

To make sure the generatedSourcesDirectory is configured as Java source
folder, we need to add a generate-sources:add-source goal, and remove
the configuration for source folder.

Change-Id: I768ed1252e0dfb32cbf67e01777f0fb578b76691

walteryang47/ovirt-engine,yapengsong/ovirt-engine,yapengsong/ovirt-engine,OpenUniversity/ovirt-engine,halober/ovirt-engine,yapengsong/ovirt-engine,yapengsong/ovirt-engine,Dhandapani/gluster-ovirt,walteryang47/ovirt-engine,yingyun001/ovirt-engine,OpenUniversity/ovirt-engine,Dhandapani/gluster-ovirt,OpenUniversity/ovirt-engine,OpenUniversity/ovirt-engine,Dhandapani/gluster-ovirt,eayun/ovirt-engine,eayun/ovirt-engine,yapengsong/ovirt-engine,Dhandapani/gluster-ovirt,yingyun001/ovirt-engine,OpenUniversity/ovirt-engine,derekhiggins/ovirt-engine,derekhiggins/ovirt-engine,Dhandapani/gluster-ovirt,yingyun001/ovirt-engine,eayun/ovirt-engine,derekhiggins/ovirt-engine,zerodengxinchao/ovirt-engine,eayun/ovirt-engine,walteryang47/ovirt-engine,zerodengxinchao/ovirt-engine,halober/ovirt-engine,derekhiggins/ovirt-engine,walteryang47/ovirt-engine,yingyun001/ovirt-engine,eayun/ovirt-engine,walteryang47/ovirt-engine,halober/ovirt-engine,yingyun001/ovirt-engine,zerodengxinchao/ovirt-engine,halober/ovirt-engine,zerodengxinchao/ovirt-engine,zerodengxinchao/ovirt-engine