This allows Cursor.proto.moveRight to avoid pre-clipping its position. It just passes the appropriate clipping options when setting its screen position.
Also factored `get(Beginning|End)OfCurrentWordBufferPosition` methods out of `moveTo(Beginning|End)OfWord` on Cursor. They are used by a `getCurrentWordBufferRange` method, which Selection now uses to find the range of the current word.
Scroll methods are now Editor.scrollTo(), Editor.scrollHorizontally() and Editor.scrollVertically()
Editor.scrollTo() can only be called once per runloop