[MPMD-344] Properties verbose and printFailingErrors are overlapping

**[Andreas Dangel](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=adangel)** opened **[MPMD-344](https://issues.apache.org/jira/browse/MPMD-344?redirect=false)** and commented

The two properties `verbose` and `printFailingErrors` do almost the same:

* verbose: Print details of check failures to build output. - this includes also violations that are only warnings and do not fail the build
* printFailingErrors: Print details of errors that cause build failure - this only includes violations that fail the build

If both options are enabled, then the violations the fail the build are printed twice.

The options should be handled more logically: If "verbose=true", then printFailingErrors can be ignored. If "verbose=false", then only print the failing errors if "printFailingErrors=true". That way, always the correct stuff should be printed.

Also the properties description (javadoc) should be improved with a better explanation.

Original issue reported here: https://github.com/pmd/pmd/issues/4001

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No further details from [MPMD-344](https://issues.apache.org/jira/browse/MPMD-344?redirect=false)