When hit, add invulnerability period and impotent period

[ashirley]

When you are shot there should be a time when you cannot shoot back (to prevent tit-for-tat) and when you cannot be shot again. The 2 times should be independent and preferably changeable by admin/console

[neothermic]

Should we reserve a colour for downed or invulnerable players, to indicate it to others?
Ideally team identity would be preserved while making it clear this person is invulnerable - flashing status LEDs?