testing: test values in their original type

Instead of using strings everywhere we can systematically test the parameters in their original type. This allows:

• to use enums by their original name instead of converting to int and then string.
• more complicated parameter values in the definition that just scalars and string i.e members of some parameter object i.e default_params.filterByConvexity

It requires to have doubles and floats entered as such but I think this is a good improvement.