Profide an ImixsDateConverter supporting empty values

[rsoika]

With the default JSF DateTimeConverter it is not possible to empty an existing value.

We should provide a custom component with this feature:

  <h:inputText value="#{workitem.item[item.name]}">
    <f:converter converterId="ImixsDateConverter" />
    <f:attribute name="ImixsDateConverter.pattern" value="#{message.datePatternShort}" />
    <f:attribute name="ImixsDateConverter.timeZone" value="#{message.timeZone}" />
  </h:inputText>

The new converter should be used in the custom forms!