Reference-value-based patterns: add feature switch all/complete cases

[TammoReinders]

For the reference-value-based patterns the display shows only those participants that have no missing values for all the selected visits. A possibility to look at the total numbers would be helpful. This would require the following tasks:

• Add a switch to switch between complete cases and all cases.
• For all cases analysis, the information about the number of missing values per visit should be somehow added to the plot.