Improved error handling in shared library import wizard

Improved error handling in shared library import wizard

Previously the wizard catched all exceptions in the wrong place causing
the UI to never show any errors to the user and just close the wizard as
if everything was successful. The problems were only printed to the
console and in selected cases also to the workspace error log.

This changes the import code to not catch any exceptions and let the UI
side deal with the thrown exceptions by logging them, showing them to
the user as the wizard's error message and in a separate error dialog.

refs #6903
[PRIVATE-12918]

Change-Id: I5014c86abb61e097b610d7f62e849d1737a4a92b