Reworked floating combat text

Floating combat text is a bit of an art-form, I think. I added a couple of features to it to make it look better.

- text gets a random offset within a small area, which makes several messages appearing at the same time look better, as they don't stack on top of one another

- added a minimum delay between messages, if a message is requested within a short time after another one - it will be delayed a bit, basically it's like a rate of fire

As a result messages look a lot nicer when many of them appear at once