- More code cleanup and codestyle updates

- Fixed some possible nullref exceptions
- Methods signatures now have up to 3 parameters before breakaing down each parameter in a separate line
- Method invocations have the same rule, except the first parameter will be in the same line as the invocation to prevent some ugliness when passing lambas as arguments
- Applied many more codestyles
- Extensions folder fully reformatted

src/NadekoBot/Db/Models/DiscordUser.cs

@@ -20,16 +20,12 @@ public class DiscordUser : DbEntity
     public long CurrencyAmount { get; set; }
 
     public override bool Equals(object obj)
-    {
-        return obj is DiscordUser du
+        => obj is DiscordUser du
             ? du.UserId == UserId
             : false;
-    }
 
     public override int GetHashCode()
-    {
-        return UserId.GetHashCode();
-    }
+        => UserId.GetHashCode();
 
     public override string ToString() => 
         Username + "#" + Discriminator;