Board Exporting

We added board exporting to Glassboard — see the write-up on MacDrifter.

We chose HTML as the first format to support. (We might offer choices in the future. And might not, since HTML is universal.)

Nick Harris did a good job on this. As I recall he had to fight some libraries to make them work with Unicode. (Which is never a fun time, and it makes me so glad to live every day in the NSString world.)