[MYC] Add scenario / session ID selection functionality to parameters

[timgassmann]

Add a column to the parameter file (Excel) on sheet "Sessions" which allows the user to specify (e.g. with TRUE and FALSE) which of the ETM scenarios provided in the list should be considered by the script when it is executed. This makes the process much more flexible / efficient by preventing always running the script for all scenarios even if no changes are made to some of them. At the same time the full set of scenarios remains visible in the parameter file. Probably adding that user modifiable column requires some adaptions in the script code which reads in the scenario / session IDs.