added some simple tests checking if all widgets are available

git-svn-id: http://dev.piwik.org/svn/trunk@7786 59fd770c-687e-43c8-a1e3-f5a4ff64c105
added method to reset widgetlist - for testing only


git-svn-id: http://dev.piwik.org/svn/trunk@7787 59fd770c-687e-43c8-a1e3-f5a4ff64c105