Quality-report

* Recent history charts for metrics are now downloaded when creating the
report instead of when the user loads the report.
* Bug fix: don't use memory address of objects when generating a stable
id of metrics for use in the history.

* The dashboard now uses column charts when displaying all versions of
products and pie charts when displaying only the trunk versions of products.

* Bug fix: strip revision numbers before passing them to Subversion.

* The dashboard now uses column charts instead of pie chart so that it can
give an overview of all product versions that are included in the quality
report.
* Introduce new quality attribute - dependency quality - and specify that the
related metrics measure that quality attribute.
* Bug fix: ignore revisions created by Maven on tags when checking for
unmerged revisions of branches.
* Bug fix: don't invoke the Sonar runner on products without Sonar id.
* Remove ART performance metric. Not used anymore.

* Bug fix: don't report the number of dependencies on snapshot versions for
the snapshot version of products.

* Add a metric for measuring the number of dependencies on snapshot versions.