Fixed numbers for series.bars.align.center and series.bars.align.right, added a font object with size, style, weight, family, color settings, optimized some code.

Please review and accept my changes. I've fixed vertical alignment of numbers in stacked bars. As you can see here http://joetsoi.github.io/flot-barnumbers/, numbers in the last two examples are not well vertical aligned. Furthermore, I added support for center and right oriented bars and added a "font" object to be able to set font specific settings. Example:

```
numbers: {
    show: true,
    font: {size: 12, style: "italic", weight: "bold", family: "Arial", color: "blue"}
}
```

I also done some optimizations like removing of duplicate code snippets.

Thanks in advance.