CTF: Add missing features

[rtxa]

Add

• Add HUD message in left side displaying both teams score and flag status: https://www.youtube.com/watch?v=h6Ryp7nb-WM
• Add DOM (Domination) mode. There are control points, and the flag turns green (we could give the flag an extra skin to make it easier to identify).

Missing

• CTF: Add missing sound announcement when flag returns by its own #42
• sv_ag_ctf_roundbased - Round based game (start over at spawn when a team caps a flag)
  • Shows HUD msg on win "Last round won by blue" then countdown "The match starts in 3, 2, 1"
• The hitbox of the flag in AG is a cube and does not cover the entire flag; check sizes and consider whether to maintain compatibility or improve it.
• Remove the delay when the flag returns to its place (Original mod practically has no delay, but I don't think that would be a good idea...).

Ideas

• Use alert system where flag status icon flickers when taken.
• Use alerts sounds like TFC to indicate better when the flag is taken, captured or dropped.
• Use HUD messages in center like TFC to indicate who stole the flag, if your team capture, right now we use print_center like AG which works similar to DeathMsg, but it's easy to miss those messages. We can also use colored hud messages (Send a HUD white and DHud message behind with blue color)
• Add chat placeholder like %F to show something more valuable like Flag status: Carried/On base/Dropped).
• Check when to add teleport effect on flag grab, return, etc.

BHL Client

• Add color support for print_center, useful to indicate flag color.