Detect not matching classes and warn/provide workaround

[mickaelistria]

When importing a report with class that don't match the ones created by JDT (same class, but different from runtime version because of pack200, ascpectJ or whatever that modified the class), then EclEmma should detect that classes as provided by JDT and as expected by report don't match. It should open a warning to explain the issue, which is difficult to guess, and ideally allow choosing some other class and jar files to generate reports. So user would be able to give to EclEmma the files classes that were used at runtime, and EclEmma would use them instead of JDT ones.

[marchof]

The same situation can also happen when running tests within Eclipse e.g. when certain mocking tools are used. Also in this case a warning should be issued.