Add simple macros for the 4 session-benchmarking methods

* This adds a companion macro for each of the 4 session-benchmarking methods.
* Instead of allowing for custom strings in the `step` method, it inserts a string with the *Class* and *Method* which is calling the macro.
* The macros are best used by inserting `MGBenchStep()` at the *end* of each method you want to track from, as that will tell you (assuming you're putting the method in most/all of your benchmarked methods) how long that method ran for.