#134 WebTester.submit() does not find submit button

[Joerg Troester]

While WebTester.assertSubmitButtonPresent() actually finds button elements of type "submit", HtmlUnitTestingEngineImpl.submit() does not.
Refer to the latter class/method line #1605. Insert the following code snippet and everything works fine:
8<---
}
inpt = getForm().getHtmlElementsByTagName("button")
.toArray();
for (int i = 0; i < inpt.length; i++) {
8<---
Explanation: a distinct lookup for button elements in the given form is needed.

[Joerg Troester]

Duplicate of #129