Left scroll

Added the uView.scrollLeft() function to match the existing uView.scrollRight(). Even though there's a TODO in scrollRight for the scroll speed, if scrollRight is currently available, we may as well have scrollLeft as well.

I didn't add scrollVertRight or scrollVertLeft. These need some consideration because they use the additional pages that the MicroView doesn't display. Besides, they don't look very useful for any real life applications.