General ErrorPage improvements

General error page improvements (includes other subtask from MYFACES-3053).

Please see attached screenshots - the tested view is:

<h:inputText id="inputText" value="#

{bean.value}" >
<f:valueChangeListener binding="#{bean}" />
</h:inputText>
<h:inputText id="inputText2" value="#{bean.value}

" >
<f:valueChangeListener binding="#

{bean}

" />
</h:inputText>

where valueChangeListener throws NPE.