xUnit test case

It seems, although it's not certain, that xUnit test result xml contains
testcases, and they may or may not have failure or error child nodes.
Added a test with such file.

It seems, although it's not certain, that this differs from Google Test
FW XML results so that Google testcases have result attribute whereas
xUnit ones do not.
Added support for xUnit test XML

Now a testcase without a result or status is considered to be an xUnit
test case, and those are considered passed unless they have failures or
errors as children.

This has an effect of accepting MeeGo test cases missing result, but
currently that does not seem to be too big of a tradeoff.
Readme updated