add horizontal origin modes to TextOrigin

Currently the x locaiton of the text node is always the left side of the rendered text. Unfortunately for more complex use cases it is needed to specify the x location as the center or the right side of the text. I suggest to add more modes to TextOrigin -> not only vertical we have so far, but also horizontal - TextOrigin.LEFT, TextOrigin.CENTER, TextOrigin.RIGHT. The default would be left. I realize TextOrigin is an enum, but perhaps it should be changed to int or we can have horizontal text origin ...