Failure to refine a path-like to a given target type should be PathWrapperException, not simple TypeError

[vreuter]

Ideally, use sites will always construct exception handling clauses as narrowly as is merited to avoid inadvertently catching exceptions of which they're not really confident of the cause. Being as that's not likely the case, though, we should always be emitting PathWrapperException when a call to refine a Path or a string as one of the types in this library fails. Right now that's the case for refinement through from_string, but not directly through a constructor. This divergence between the code paths traveled for refinement is a further issue that should be solved.