Support multiselection

[PhilippSalvisberg]

The extension supports currently only single selection. When selecting multiple items in the Connections navigator tree the Run utPLSQL test menu item is disabled explicitly. However, it would be useful to support multiple selection independent of issue #6.

[PhilippSalvisberg]

Here's an example how to execute two test packages:

SET SERVEROUTPUT ON SIZE UNLIMITED
EXECUTE ut.run(ut_varchar2_list('PLSCOPE.TEST_ETL', 'PLSCOPE.TEST_DD_UTIL'));

ut_varchar2_list should be used only if more than one object is selected.