Made turrets use projectile-appropriate SFX

Fixes #5030
Add changelog.yml
Fixed comment to reflect reality

Spent 2 hours working out how turrets create sounds before figuring out
that I'm an idiot.
Turret SFX and spawning changes

* Turrets now use the SFX associated with the weapon installed in them
* Turrets now have a default installed gun for when they are spawned
* fire_sound is now a property of all ammunition, not just energy ammo,
which should make future additions a lot simpler.
* Added some energy gun SFX handling to the giant switch statement at
the top of portable_turret.dm, because 'emagged' and 'lethal' are the
same thing and have to be handled weirdly.
* The upshot of all these changes is that every turret, constructed or
default, should make exactly the right noise, even if guns are added in
the future!
Remove changelog
Merge pull request #5120 from nivomi/turretsounds

Make spawned turrets use projectile-appropriate SFX