Add new layer for Venus cloud layers (closes #1534)

data/assets/scene/solarsystem/planets/venus/layers/colorlayers/venus_texture.asset

@@ -4,9 +4,15 @@ local texturesPath = asset.syncedResource({
   Name = "Venus Textures",
   Type = "HttpSynchronization",
   Identifier = "venus_textures",
-  Version = 1
+  Version = 2
 })
 
+local clouds = {
+  Identifier = "Clouds",
+  FilePath = texturesPath .. "venus_clouds.jpg",
+  Enabled = asset.enabled,
+}
+
 local layer = {
   Identifier = "Texture",
   FilePath = texturesPath .. "venus.jpg",
@@ -18,20 +24,23 @@ local layer = {
 }
 
 asset.onInitialize(function()
+  openspace.globebrowsing.addLayer(globeIdentifier, "ColorLayers", clouds)
   openspace.globebrowsing.addLayer(globeIdentifier, "ColorLayers", layer)
 end)
 
 asset.onDeinitialize(function()
   openspace.globebrowsing.deleteLayer(globeIdentifier, "ColorLayers", layer)
+  openspace.globebrowsing.deleteLayer(globeIdentifier, "ColorLayers", clouds)
 end)
 
-asset.export("layer", layer)
+asset.export(layer)
+asset.export(clouds)
 
 
 
 asset.meta = {
   Name = "Venus Texture",
-  Version = "1.0",
+  Version = "2.0",
   Description = "This asset supplies a default texture for Venus",
   Author = "OpenSpace Team",
   URL = "http://openspaceproject.com",