feature: KZ Timer

[khanghugo]

Almost all KZ maps use these "target" for timer start and end.

  "counter_start",
  "clockstartbutton",
  "firsttimerelay",
  "but_start",
  "counter_start_button",
  "multi_start",
  "timer_startbutton",
  "start_timer_emi",
  "gogogo",
  "startcounter"

  "counter_off",
  "clockstopbutton",
  "clockstop",
  "but_stop",
  "counter_stop_button",
  "multi_stop",
  "stop_counter",
  "m_counter_end_emi",
  "stopcounter"

Would be nice if we have that for BXT.

The problem right now for me is that CBaseButton::ButtonUse does not work on Linux. I have had this problem before. If it is possible to just find whether a "target" is hit then it should be fine.