Added some comments.
* sample.trx: Added categories to sample.trx.

* MSTestResult.cs: Added constuctor overload that doesnt require a
  test suit and uses null as deault.

* TRXParser.cs: Commented out the default category setting for tests
  without suits.

* TRXParserTests.cs: Fixed TestCategoriesWereFound test.
* TRXParserTests.cs: Removed null check.

* AllureAdapterBase.cs: Added empty suite handeling.

* MSTestResult.cs: Added empty array handling to constructor.
* TRXParserTests.cs: Added TestOwnersWereFound test.

* sample.trx: Added owner elements.

* AllureAdapter.cs: Fixed parameter to TestFailed call.

* AllureAdapterBase.cs: TestStarted copies owner data.
Test Started/Failed/Finished methods now get a MSTestResult instance
  instead of the different members.

* MSTestResult.cs: Added owner field.

* TRXParser.cs: Added owner parsing from trx file.