add xUnit save each source file in an own test result file

I added every source file creates a own xUnit result file.
If you set 
```
<xUnit>/a/b/c/result.xml</xUnit>
```
and the test "test1.js" and "test2.js" exists the result files are
/a/b/c/result-test1.js.xml and /a/b/c/result-test2.js.xml