Rules updates and clarifications

I received some awesome feedback when working on Aphelion Transit, the sci-fi version of this game. So I took that feedback and applied it here as well. This is a quick summary of the changes:

• Max Hits/Injuries/Current Hits was confusing. It is now Health/Injuries/Hits. Health represents the number of hits the character can take before being KO'd. Hits accumulate into an injury. Such a simple change made things much easier to understand.
• Characters now die after 3 untreated injuries.
• A characters health can be increased only 3 times.