Issue 13 Completion

Fixes issue #13.

This completes the items, which were left undone in an earlier merge request. See #13 for a list of all the items included.

The commits below make the following changes to NUnitLite, to match nunit-console...

1. Modify --test to take a comma-separated list of values.
2. Modify --explore and --result to take output specifications
3. Add tests of --include and --exclude options

Note that the implementation of --include and --exclude for both NUnitLite and nunit-console allow comma-separated lists of categories but _not_ category expressions as implemented in NUnit 2.6. We have some design work to do to define a dsl for  selecting tests.
Ah! The test comes from NUnit 2.6 or nunit-console and uses System.Xml.XmlNode. Framework uses NUnit.Framework.Interfaces.XmlNode so it has to be converted. The conversion is not as simple as it is in some other cases. For now, I'd like to move on, so I added a TODO to the code to remind me of why it's not run the next time I look at it.