1174 Use DIVI data to scale initial values for LCT model (#1175)

- Method to calculate an initial value vector for an LCT model using reported RKI data now provides the option to scale the result so that the number of ICU patients equals the reported number in the DIVI data set.
- Added tests. 

Co-authored-by: annawendler <[email protected]>

Author: lenaploetzke