Altered changes view to hide excluded commits

The main build view now have excluded changes hidden by default (and a linke *Show 15 hidden*) to show them. Excluded changes, when shown, are grayed to make them look different from included changes.

I have not found any *true* way to get GitSCM to analyze the changes, whether they are excluded or not.

Also the suggested implementation only supports projects with a single git SCM. MultiSCM is not supported, because, I have not found any way to detect which SCM the certain change belongs.

I had some problems with embedded HtmlUnit. So, some tests should be activated only after HtmlUnit is upgraded to modern version.