Add verifications in XML and HTML reports

[Galad]

Requires #35

Verification results should appear in the XML and the HTML reports.

For XML in should have the following result:

<then start-date="01/01/0001 00:00:00 +00:00" end-date="01/01/0001 00:00:04 +00:00" duration="4844" result="failed">
     <question start-date="01/01/0001 00:00:00 +00:00" end-date="01/01/0001 00:00:04 +00:00" duration="4844" name="Displayed items" has-error="false">
       ...
     </question>
     <outcomeDetail>
         <![CDATA[Assert.Equal() Failure
                                 ↓ (pos 44)
Expected: ···d4-8758-6900b09593a0
Actual:   ···d4-8758-6900b09593a0!
                                 ↑ (pos 44)]]>
     </outcomeDetail>
</then>

Possible values for the result attribute are passed, failed and error.
The element outcomeDetail will be empty the the result is passed, otherwise it will contains the exception message.

• Add verification in the XML report
• Add verification in the HTML report