Way better handling of calling functions from CSHarp

UpsilonTests/FunctionTests.cs

@@ -151,5 +151,20 @@ a = 87
             Assert.Equal(60, (long)(NumberLong)result);
         }
 
+        [Fact]
+        public void ReturnFromCSharpCall()
+        {
+            const string input = @"
+function testFunc ()
+    return 100
+end
+";
+            var script = new Script(input);
+            Assert.Empty(script.Diagnostics.Messages);
+            var result = script.EvaluateFunction<NumberLong>("testFunc");
+            Assert.Empty(script.Diagnostics.Messages);
+            Assert.Equal(100, (long)result);
+        }
+
     }
 }