Install test to control TP version used at install time
    Status: updates/kepler is still 4.30.5.Alpha3
    Dev site http://download.jboss.org/jbosstools/discovery/nightly/core/trunk/ links to http://download.jboss.org/jbosstools/updates/kepler/ which links to ../../targetplatforms/jbosstoolstarget/4.30.5.Alpha3/REPO/
    When to update it? It's required to change it for correct installation tests

    Time to update: after Alpha2 is no longer the defacto release? Did you want all those users to break suddenly? ~nboldt
       No, you can do install tests using the discovery site: 
       http://download.jboss.org/jbosstools/discovery/nightly/core/4.1.kepler/compositeArtifacts.xml (contains the correct version of JBT, TP, and Extras for 4.1.kepler stable branch (which is currently Beta1)

    Suggestion 0 (Mickael): Can't we directly use url http://download.jboss.org/tools/targetplatforms/${tpc.version}/REPO in aggregated site?
       We could, yes. https://github.com/jbosstools/jbosstools-build-sites/blob/master/aggregate/site/pom.xml#L33 However, that means we would need to keep old TP sites around longer (?)
       At least keep TP releases forever
       Drawback: Static link to static URL will make Eclipse keep reference to older site even if we are updating

    Suggestion 1 (Max): use relative path for references in aggregate site
       example:
         core/trunk/  -> p2 ref to ./tpc   (assumes relative link works for p2.??? <-- what property is it?) => It's the "repository" element inside "references" in content.jar/xml (on site) and in https://github.com/jbosstools/jbosstools-build-sites/blob/master/aggregate/site/pom.xml#L33
         core/trunk/tpc -> composite link to TPC  (will be ${tpc.version}/REPO in ci's, but gets updated to updates/kepler on staging
       Sounds good, but p2 does not accept relative reference 
    Suggestion 2 (Max): Test composite
            https://jenkins.mw.lab.eng.bos.redhat.com/hudson/view/DevStudio/view/DevStudio_7.0.kepler/job/jbosstools-composite-install_41/ tests http://download.jboss.org/jbosstools/builds/staging/_composite_/core/{trunk,4.1.kepler}/
            Then nothing tests the aggregate site, which is error prone => Not good

    Suggestion  3 (Nick): Using different "quality" sites for references (just like JBDS)
         TODO: generate TWO aggregates: one w/ references to TP, one with none
         http://download.jboss.org/jbosstools/updates/kepler/  <-- each stable milestone and release
         http://download.jboss.org/jbosstools/updates/kepler/staging/ <-- use this for QE
             End users want one site w/ all TP refs embedded (one site does everything)
             Max thinks QE wants a site that has NO references so it's easier to test 
         For JBDS we use this:
            https://devstudio.jboss.com/updates/7.0-staging/ (QE pre-milestone)
            https://devstudio.jboss.com/updates/7.0-development/ (latest milestone)
            https://devstudio.jboss.com/updates/7.0/ (eventual GA)
         And when installing, this happens:
            https://svn.jboss.org/repos/devstudio/trunk/product/features/com.jboss.jbds.product.feature/p2.inf

    Suggestion 4 (Max):
         Generate aggreate WITHOUT references to TP
         Generate composite that references ^^^ + TP <==    
         No reference is the only valid long-term solution

    Suggestion 5 (Max & Mickael): Allow more control on install-grinder to ensure we can explicitly use right sites
        install-grinder --site http://download.jboss.org/jbosstools/discovery/nightly/core/trunk/  --site  http://download.jboss.org/tools/targetplatforms/${tpc.version}/REPO
        ACTION: Mistria, makes
            install-grinder --removeAllSites --addRef http://download.jboss.org/tools/targetplatforms/${tpc.version}/REPO --installSite http://download.jboss.org/jbosstools/discovery/nightly/core/trunk/
            @Pavol already did something for that: https://github.com/jbosstools/jbosstools-install-grinder/blob/master/plugins/org.jboss.tools.tests.installation/src/org/jboss/tools/tests/installation/AddSiteTest.java
        Pitfall: Not perfect util we stop setting references in aggregate.