TextBlock style update 

Hi all,

This one passes tests and I ran through a few samples and it seems to behave as expected!

I did make a bunch of changes that I'll comment on inline which should be reviewed. I'm pretty sure this can be improved in a couple of places but I'm not sure how.

@jasonrclark I'm not sure how this should mix with #832. Based on what I see I think they should play nicely.
The way that `Common::Style` works now makes it so that any kind of default styling needs to go in the `STYLES` constant of the class, and *not* get passed in as an argument. So I reshaped how this works a bit.