Merge JUnit run and Jacoco

[mauricioaniche]

Currently, we first run junit and then jacoco. This implies in running the tests one more time than needed. We can combine both steps in one.

This means we'd change our weblab buttons to:

• Run with coverage, which will run junit and jacoco
• Run mutation, which is more expensive

That can even be a good thing in terms of load, as most of the times students need the coverage and not the mutation report.

The overhead of coverage isn't that large, so we can run together with the first step.