return faultdetail on soap fault

NOTE: this _might_ cause issues for code that simply checks whether the
return value is true-ish.
Update/fix/improve Soap Fault handling

the ProPS API method no longer returns the SOAP Fault detail,
but returns undef. The get_error will return the error as a string
(including the type, code, and description).
The new method get_fault returns the ServiceException->ExceptionItems
(there is no longer an ExceptionItem underneath that, except
perhaps when there are multiple errors?); the returned value
is { errorCode=>'digits', errorType=>'B', errorMessage=>"...." }.