Typo, redundant string interpolation, namespaces and imports cleanup (#2068)

* Readonly, typos and redundant string interpolations

* Namespaces

* Optimize imports

* Address reviews

* but actually

* Localize missing strings

* Remove redundant vars

Content.Server/GameObjects/Components/Atmos/AtmosExposedComponent.cs

@@ -1,6 +1,5 @@
 using Content.Server.Atmos;
 using Content.Server.GameObjects.Components.Temperature;
-using Content.Shared.Atmos;
 using Robust.Shared.GameObjects;
 
 namespace Content.Server.GameObjects.Components.Atmos