Test suite element linking from JUnit runner

Implement linking for TestSuiteElements in the JUnit test runner for suite/feature/spec on double-click.

Also:
* fixed so the open test action will compile/run on luna/mars target platforms (as well as kepler)
* fixed the Run As... suite element selection for .feature files so it matches the open test action (by using the selected scenario if the cursor is in the scenario header line)