fixes on ratio_over
fix Flow::extrusion_width (bad computation of first_layer_height)
fix enum visibility
moving test classes to prusaslicer test directory (wip)
all that because i was trying to write a test class for a modification in min_object_distance (and i didn't even start)
Extended ConfigBase with set() functions similar to the upstream Slic3r.
ConfigBase::set_deserialize() newly throws if the operation fails.
Extrusion width parameters are newly tested for negative values.
