Rider static analysis (#433)

* Non-accessed local variable

* Merge cast and type checks.

* StringComparison.Ordinal added for better culture support

* Supposed code improvement in launcher. Remove unused code.

* Update ExplosionHelper.cs

Unintentional change.

* Optimized Import

* Add Robust.Shared.Utility import where it was deleted

* Other random suggestion

* Improve my comment

Content.Client/ClientNotifyManager.cs

@@ -2,7 +2,6 @@ using System;
 using System.Collections.Generic;
 using Content.Client.Interfaces;
 using Content.Shared;
-using Robust.Client;
 using Robust.Client.Interfaces.Console;
 using Robust.Client.Interfaces.Graphics.ClientEye;
 using Robust.Client.Interfaces.Input;