Revert Text to 0.7-version (Fixes #137)

If onAttach/onDetach are not overridden then those are called from widget where
DOM.setEventListener(getElement(), this);
is called.
This method is apparently not available for text nodes in IE8.
Conflicts:
	core/src/main/java/com/dianaui/universal/core/client/ui/html/Text.java