Removed uses of deprecated jQueryMobile APIs.

* Replaced use of $.mobile.changePage with pagecontainer's change event.
* Replaced use of data-role="content" with ui-content class.
* Replaced use of data-role="fieldcontain" with ui-field-contain class.
* Replaced use of data-role="content" with ui-content class.
* Replaced the filter extension with the Filterable widget.

Also replaced button markup for anchor tags with CSS classes.
Upgrade to GWT 2.6.1
updated WFK and EAP BOMS to 6.2.2.GA and 2.6.0-build-1 versions
Update CONTRIBUTING.md

Correcting the fork link for DEVELOPER-410
https://issues.jboss.org/browse/WFK2-613 removed also remaining files in helloworld-errai
added Super Dev Mode options into GWT module descriptor and added an appropriate description into README.md file