Rename 7.5_trunk job to 7.6_trunk job; fix linkages within composite site

When moving from 7.5 in trunk to 7.6, need to:

a) rename the Hudson job: http://hudson.qa.jboss.com/hudson/job/jbosstools-teiid-designer-7.5_trunk/
b) ensure the new job is listed here: http://hudson.qa.jboss.com/hudson/view/DevStudio/view/DevStudio_Trunk/
c) ensure the newly named job builds
d) edit these files:

http://anonsvn.jboss.org/repos/jbosstools/trunk/download.jboss.org/jbosstools/builds/staging/_composite_/trunk/compositeArtifacts.xml (teiid 7.5 job output appears twice, intentionally)
http://anonsvn.jboss.org/repos/jbosstools/trunk/download.jboss.org/jbosstools/builds/staging/_composite_/trunk/compositeContent.xml (teiid 7.5 job output appears twice, intentionally)