Overloads of WriteNode and WiteNodes that take expressions #49

Currently, simple calls to WriteNode and WriteNodes look like this:

WriteNode("SwitchValue", expr.SwitchValue);
WriteNodes("TestValues", switchCase.TestValues);

We could have an overload that takes an expression, then calls would look like this:

WriteNode(() => expr.SwitchValue);
WriteNodes(() => switchCase.TestValues);

and resolve the path by parsing the expression tree.

We'd want to investigate potential costs of constructing these expression trees at runtime.