Remove hard-coded IsProtected flag on LibraryContainer

- Default FileSystemContainers to IsProtected = false
- Issue MatterHackers/MCCentral#2420
DragDrop zip onto bed suggests it works but does not

Library/Providers/FileSystem/FileSystemContainer.cs

@@ -55,6 +55,8 @@ namespace MatterHackers.MatterControl.Library
 			this.fullPath = path;
 			this.Name = Path.GetFileName(path);
 
+			this.IsProtected = false;
+
 			this.ChildContainers = new List<ILibraryContainerLink>();
 			this.Items = new List<ILibraryItem>();
 #if !__ANDROID__

Library/Providers/LibraryContainer.cs

@@ -46,7 +46,7 @@ namespace MatterHackers.MatterControl.Library
 		public Type DefaultView { get; protected set; }
 
 		public List<ILibraryContainerLink> ChildContainers { get; set; }
-		public bool IsProtected => true;
+		public bool IsProtected { get; protected set; } = true;
 
 		public virtual Task<ImageBuffer> GetThumbnail(ILibraryItem item, int width, int height)
 		{