Add a second facebook comments block

We have a case where we are using the block in two different panel configurations. One is wide and the other is narrow. I have attached a patch that allows a secondary FB comments block that can have different settings (# of comments, width, color) whil sharing the same global settings.

I don't know if this is worth including in the actual contrib module (though it would be handy for some), but I'm attaching the patch here in case someone else needs something similar.

Note: I have moved the block content code into a function that runs from the delta. This should make it much easier to add any additional blocks with just a few changes.