Extend stage table generation to enforcre and use traget same target column type

[mattywausb]

Since a good practice woul be, to do all type conversions from source to stage, the stage table must use the target column types in its own columns.
This can result in two different behaviours.

1. raise an error, when not all mapped target columns for a stage column have the same type
2. create multiple stage columns for every target type needed

since teh 2nd is very rare, we will implement the 1st first.

• concept documentation adapted
• function tests added
• check tests added
• Model profile syntax extended with "use_target_type_in_stage"
• dvpdc extended
• decided if we will put method 2. on our feature list