New Containment Breach gamemode

This is the gamemode where SCP validhunts you !

Since it's all brand new and fun, I'll just give a simple idea :

- SCP-173 is the main antagonist of this gamemode. For now. He'll most
likely stay this way, but more SCP/hostiles might be added
- SCP arrives via teleportation (near a vent, but hell). He immediately
triggers an EMP and a biohazard alert fires to rile up the crew (also,
this acts as a pretty malicious counter-metagame to Blob)
- After a few more minutes, SCP's presence is revealed. From there,
random events (justified by a takeover from SCP-079) run to make
everything much more complicated
- SCP-173 goes around fucking shit up. The goal is to get rid of him,
which is theorically done via teleporting
- If the crew is not done in a fair amount of time, both from SCP-173
wrecking shit and SCP-079's influence fucking up people, it (SCP-079)
breaches into the station's systems and arms the nuke Malfunction-style.
This is the loss condition

Further notes :

- There are comments for special announcement sounds. Uncomment then
after the announcements.txt file is generated
- This is a functional draft. Might see improvements and changes
- The goal is to make a gamemode that can pop up on Secret from time to
time. It might evolve into a more general spook round
- Yes, I know about the spawn() staircase. It has no effect on performance (IN THEORY), at worst it makes the code more annoying to browse
There's likely better ways to handle this, but that'll be dealt with later (admin control and interaction should wait until everything is good and stable)