Added new theme that mimics maven surefire plugin

[msiemczyk]

Since the plugin does not provide a way to define the test summary I've
added new themes (maven and maven-plain) and that inherit from
standard and plain themes repsectively but override summaryText to format it the way
maven-surefire(and failsafe)-plugin used to do it maven. I've also
updated unit tests so their passing again and added some new tests for
new classes.

Differences with maven plugin:

• added the Time Elapsed to "Test Run: " line
• changed "Results:" to "Summary:" as Gradle build outputs errors before
  Summary (maven includes errors in Results section).

Ideally the plugin provide a way to customize how the summary text looks like, but this will be harder to implement in a generic way that would satisfy everyone needs.

[radarsh]

Hi, this is great - thanks for contributing. Do you have a screenshot handy that shows what the generated output would look like? If not, no worries and I'll check it out later.

[msiemczyk]

I do. I will provide them in couple minutes.

[msiemczyk]

Maven theme (colours):

Everything good:

Skipped tests:

Failed tests (and skipped):

Maven plain theme just removes the colours and formatting so we can use that Jenkins console.

[msiemczyk]

@radarsh are you not okay with these changes being made? If not I will have to build custom version of the plugin and deploy to our own local repository so I just need to know if you going to apply these changes to your plugin or not.

[radarsh]

@msiemczyk just held up with a few things. I haven't had a chance to look at this PR in detail yet.

[msiemczyk]

@radarsh did you have a chance to look at my PR?

[radarsh]

@msiemczyk I'm sorry but no. You'll hear from me when I have had a look. Appreciate your patience.