[JENKINS-6876] Create a dash-board view portlet that shows the SLOC of the selected projectes
[JENKINS-12166] add a sloccount portlet to dashboard

- Optional dependency to dashboard-view added.
- SLOCCount dashboard-view portlet implemented. It displays a sortable table with number of lines, files and languages for each job.
- Programming language specific data were not added to the table because there can be many of them which would break the layout. The [job x language] table would have both many rows and many columns.
- Germal and Japanese localization blindly copied from other jelly files.