revert "multisampling by default"

* It's good to be consistent in how openFrameworks renders things from version to version.
* OF users often use Processing and expect it to behave similarly (e.g., smooth() turns on smoothing, otherwise things are aliased)
* The definition of a "center of a pixel" varies, which means a white outlined rectangle (or any other 1 px shape aligned to the pixel grid) can appear gray/semitransparent instead of white.
* It's not easy enough to turn off the multisampling yet. I would concede "multisampling by default" if the meaning of "ofEnableSmoothing()" changed to be something about multisampling, or if there's another function that's added that can be used in `main()` to set the samples in a way that works with RPi.