Fix testEmptyPath test for TargetPanel.
Added possibility of a warning in the form of a yes/no question.
New prompt has been added since it seemed like this is what the test was
trying to convey, for example the message printed out is "Target.warn".
Fix the testNotWritable test in TargetPanel.
Ensure to get the actual root directory rather than the root of the
Temporary folder. Temporary folder overrides the getRoot method.
Merge pull request #264 from mtjandra/IZPACK-1153

[IZPACK-1153] - Fixing GUI Target Panel Tests