Update UiBinder xsd to include gss attribute.

A new attribute named gss has been added to <ui:style> in UiBinder.
We need to update the xsd  in order that IDE uses this information to
 automatically insert that attribute in the autocompletion.

Change-Id: I3ce96dfa20a4bc8beb9df770bdcda30e54dbe545
Display Java method and class names in chrome dev tools.

Chrome dev tools support renaming of functions in compiled
JavaScript by adding a property called displayName to the function.
Throughout dev tools this name will be used instead of the JavaScript
function name, improving the expierence in the debugger, profiler and
timeline.

Change-Id: Ic5d29b7b15772ac996bd6cb310d1370bc28c4d70
Use gwt-user-sources.jar as gwt-servlet-sources.jar for Maven.

Sonatype requires a sources jar, and gwt-servlet doesn't include sources
(on purpose) and our script to create sources jars just extracts the
sources from the jar, so it doesn't create one for gwt-servlet. Our
workaround is thus to just reuse the source jar for gwt-user as
gwt-servlet is basically a subset of gwt-user.

Change-Id: I2b6b529a730c92cd1a6b25cb3609eb6d08744714