updated Giant pyramid to have hidden selections

updates some broken collision on "Necron Gateway"

Update 19 HOTFIX:
Updated editor previews, more accurate and for the rest.

Updated Necron Gateway Portal, units thought they where better as they could see through but alas not shoot through. Now they can't see through but they can shoot through.

Removed pathing on gateway, units would walk in circles.

Added new composition: Necron Gateway
Added a new object: Necron Medium Platform.
Ajusted editor subcategory's

1). 2 new objects "Necron Small Floating Object", "Necron Medium Ground Platform"
2). complete retxture on most objects
3). glow on most objects

1). added new editor icon to ""Necron Giant Pyramid"
2). added farther distance to "Necron Giant Pyramid"

1). added new "Necron Giant Pyramid (No collision)" - theres no collision engine limitation sorry.
2). updated subcatagories

New steam pictures

1). updated and added object previews
2). added new "Necron Medium Stairs"

1). added new "Necron Large Stairs"
2). updated subcatagories with unique naming
3). updated "Necron Large Stairs With Bottom" size classification to large