Added my changes to the HCP.

Info I added:
- player and objectives section
- basic fps controls section
- traps and triggers system section
- constant change enemy section
- fixed a bunch of grammar/spelling errors

I took a look at the High Concept template Taso provided us with. We
aren't too far off from what our document should look like. However, we
don't need a section about what each team member does, therefore I
didn't add that.