start support for GWT 2.6.0
more unit test fix with gwt 2.6.0
Drop support for GXT 2  which is not compatible with GWT 2.6.0 (http://www.sencha.com/forum/showthread.php?275759-GXT-2.2.6-2.3-with-GWT-2.6)
update gwtbootstrap to lastest stable version
update google-gin to lastest stable version
fix last broken unit tests with gwt 2.6.0 in core module
update ignore list
temporarily remove gwtbootstrap support : it seems not to be compatible with gwt 2.6.0 yet (?)