Added abstraction on the test result provider.
Test aggregates are now retained.

Test parsed from the TRX that hold inner tests (like data driven tests) are returned as is and the adapter code distinguished between the two.
Merge changes from master
TRXParser was refactored out of the adapter.
Changed linq code to Min/Max instead of Aggregate.
* MSTestResult.cs: MSTestResult's suits changed to IEnumerable.

* TRXParser.cs: ParseErrorInfo get's parent for consintency and
  ToUniversalTime calls were removed.

* AllureResultsUtils.cs: Added ToUnixEpochTime call instead of the
  TRXParser.
Renamed loop variable.
Refactored TRXParser to pass data along instead of reparsing it on
recursive calls.
Moved description formatting into method.
Merge branch 'master' of https://github.com/allure-framework/allure-mstest-adapter