Allow message object on HTMLForm::setWrapperLegendMsg/setSubmitTextMsg

When a message needs plural support, it should be possible to parse a
message object with the params set.

Change-Id: Ifb67952b589a1821cde452b2be3f327f24e6b534
Merge "Allow message object on HTMLForm::setWrapperLegendMsg/setSubmitTextMsg"