Silo Fill Type Limiting

To make the game more realistic, this mod limits the number of different fill types that can be stored in a silo at the same time.
By using silo extensions, this number is increased.

Version 1.1:
* Configuration file in the “modSettings” folder is created after the first save
* Default for the maximum number of fill types per silo can be changed
* Default for number of additional fill types per silo extension
* The maximum number of fill types can be explicitly specified per silo type (optional, -1=default) (list is extended by the current relevant silos on the map when saving)