Improve logic for file and data set pattern fields

[paulcheeseman]

This change improves the UI logic for the "dump file pattern" (file) and "data set pattern" (dsn) dump options, based on the following rules:

1. Only the system dump agent is compatible with the data set pattern field
2. Dump file pattern and data set pattern cannot be specified at the same time

(The data set pattern is only applicable for z/OS SYSTDUMPS, but this distinction isn't made in the tool.)

Previously, the tool enabled the data set pattern field only if the system dump agent was enabled, but it did not prevent the data set and dump file pattern fields being specified simultaneously - it treated this situation as an error condition and displayed some appropriate text.

With this patch the rules are completely enforced by the UI, which prevents the user from creating an invalid Xdump option. If the user gets into a situation where both pattern fields contain text and both are applicable to the enabled dump types, the dump file pattern (file) option will take precedence.