Review and fix Marketplace Packages maintenance branches

Some MP are not properly aligned on the latest HF.
For instance, http://qa.nuxeo.org/jenkins/view/reports/job/addons_FT_nuxeo-template-rendering-5.8/ fails because marketplace-template-rendering is still aligned on 5.8.0-HF01-SNAPSHOT whereas it requires a fix from 5.8.0-HF06-SNAPSHOT.

Update MP maintenance branches:

• 5.6.0 => 5.6.0-HF41-SNAPSHOT
• 5.8 => 5.8.0-HF30-SNAPSHOT
• 6.0 => 6.0-HF06-SNAPSHOT

While NXBT-702 is not resolved, that must be manually managed!

In the mean time:

• check the maintenance branches stated in https://github.com/nuxeo/integration-scripts/blob/master/marketplace.ini ; update the branch names to follow the policy x.y_X.Y with x.y the minor version of the package and X.Y the related platform LTS version.
• improve the target platform: set the base target platform + the current snapshot + the hotfix target
  src/main/resources/package.xml

     <platforms>
  +    <platform>cap-5.6</platform>
  +    <platform>cap-5.6.0-HF*</platform>
       <platform>cap-@DISTRIB_VERSION@</platform>
     </platforms>
  

• create missing QA jobs