Add Character / Letter Spacing to MigraDoc

[eXpl0it3r]

Character / letter spacing is quite a common text rendering feature. For example a heading or title in Microsoft Word will be condensed by 0.5pt. MigraDoc currently doesn't offer a way to set the character / letter spacing and also doesn't allow the user to hook into the rendering code to implement some custom renderings.

[eXpl0it3r]

I guess it's worth pointing out, that some fonts have a condensed variant of their font, so in those cases, one could try to swap the font for the given paragraph.