GWT Super Dev Mode

According to release notes for GWT 2.6.0 the GWT Developer Mode will no longer be available for Chrome sometime in 2014 [1], I've replaced the description of standard Dev Mode with a description of the new Super Dev Mode [2]. I've also added necessary configuration lines into the .gwt.xml file to enable Super Dev Mode.

[1] http://www.gwtproject.org/release-notes.html#Release_Notes_2_6_0
[2] http://www.gwtproject.org/articles/superdevmode.html