Add a "hidden fields" parameter to BeanEditor and BeanEditForm

A "hidden fields" parameter would allow code like this:

<t:beaneditform t:id="form" object="person" submitLabel="Save" hidden="version"/>

instead of this:

<t:beaneditform t:id="form" object="person" submitLabel="Save">
<!-- Include version in the form to prevent it being updated/refreshed in onActivate(), which would defeat optimistic locking. -->
<t:parameter name="version">
<t:hidden t:id="version" value="person.version"/>
</t:parameter>
</t:beaneditform>

Please note this is not the same as using remove, eg:

<t:beaneditform t:id="form" object="person" submitLabel="Save" remove="version"/>

which in this example would defeat optimistic locking because version's value would no longer make the round-trip to the client.

In case it helps, here's what onActivate() might looks like in this example:

private Long _personId;

@Persist("flash")
private Person _person;

void onActivate(Long id) throws Exception {
_personId = id;

if (_person == null) {
_person = getPersonService().findPerson(_personId);

if (_person == null)

}
}