PL: updated docstring quotes and other recommended changes

Now set to use triple double-quotes and added recommended spaces. Also added a recommended "super()" method on the SiemensWrapper.__init__
RF+TST: updated multiframe error handling and tests

Necessary attributes from a multiframe stack are now checked for and raise wrapper errors if minimal information is not present. Some additions to the MultiframeWrapper docs and reworking of the tests, such that wrapper errors are checked for based on minimal metadata.