#1462 extracted MapGrid's HasGravity property to separate Content com… (#4200)

* #1462 extracted MapGrid's HasGravity property to separate Content component

* #1462 - PR suggestions

* Merge to master

Co-authored-by: metalgearsloth <comedian_vs_clown@hotmail.com>

Content.Shared/NetIDs/ContentNetIDs.cs

@@ -99,6 +99,7 @@ namespace Content.Shared.NetIDs
         public const uint DISASSEMBLE_ON_ACTIVATE = 1089;
         public const uint LIGHT_REPLACER = 1090;
         public const uint SINGULARITY_DISTORTION = 1091;
+        public const uint GRAVITY = 1092;
 
         // Net IDs for integration tests.
         public const uint PREDICTION_TEST = 10001;