survey/study: enter detailed response figures for panels surveys

[UteH]

after #1416 and #1368 we want to add some more survey information but shown and editable on the study page.

• at the moment we store separately in each survey the information shaded in yellow:
  • Panel
  • cross-section
• we want to add fields shaded in white for studies with more than one survey
• we want to enter the numbers in a table
• we want to export the information for the methods report
• we should discuss which of these information should be displayed in the MDM
  • all figures: as a table on the study page
  • yellow figures as now; do not display white figures

[rreitmann]

Currently we do not have a correlation between the surveys which is a requirement to compute the white cells in the table above.