Add Support For TF2's Player Destruction

[caxanga334]

Implement support for TF2's PD game mode.

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AI Behavior

• Collect Points
• Drop Points
• Seek and Destroy Opposing Team's Leader

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Notes

• Points are item_teamflag entities.
• To check if a player is carrying points, check if a valid entity exists in CTFPlayer's m_hItem netprop.
• To check how much points a flag is worth, check the CCaptureFlag's m_nPointValue netprop.
• The CTFPlayerDestructionLogic's m_flCountdownEndTime netprop stores the next time the portal will open.

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To-Do

• Figure out how to tell if the "gate" to the capture zone is open.