Fix for #285

With a ParameterizedTest it is possible to generate test case names with invalid XML characters. E.g.

@ParameterizedTest
@ValueSource(strings = {"Weird\bname"})
void testFoo(String input) {
    ...
}

The test case name is derived from the input string, which in this case contains an invalid XML char \b. When tools (like IDEs) try to parse the junit XML, they'll fail due to the invalid char.

Fix it by escaping test case names. It looks like test suite names could also contain invalid XML chars, so I'm escaping those as well.