Integrate JaCoCo-Coverage-Column plugin

For Emma, there is a separate plugin "EmmaCoverageColumn" which provides an additional column with coverage numbers in the dashboards on the main page. I ported this functionality to the JaCoCo plugin. 

Discussion on the mailinglist indicated that it would be best to include this functionality directly in the JaCoCo plugin. 

These commits add this functionality to the plugin for JaCoCo.