Move RubberduckTests to new csproj format

drop remaining artifacts of csproj ignoring some files and the output-directory copy behaviour being different

Author: Vogel612

RubberduckTests/Grammar/VBAParserValidityTests.cs

@@ -37,7 +37,7 @@ private void AssertParseResult(string filename, string originalCode, string mate
         private IEnumerable<Tuple<string, string>> GetTestFiles()
         {
             var basePath = Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location);
-            basePath = Directory.GetParent(basePath).Parent.FullName;
+            //basePath = Directory.GetParent(basePath).Parent.FullName;
             return Directory.EnumerateFiles(Path.Combine(basePath, "Testfiles//Grammar")).Select(file => Tuple.Create(file, File.ReadAllText(file))).ToList();
         }