Add report element

To add a report element, for example `text with info` (count number of respondents on a question):

Make the new report element known to the system

controller/ReportElementController: add case 'text with info'
forms/ReportElement/Add.php: add type 'text with info'

Define the needed information:

forms/reportElement/Edit/TextWithInfo.php: wich info do you need for this report element
application/views/helpers/ReportElement.php: which info do you want to show in view report
application/view/scripts/report/jrxml/subreport/textWithInfo.phtml: add subreport definition

(the actual subreport was already defined)