Docs and examples for RenderableBoxGrid (#3479)

* Add boxgrid examples

* Add description about the box grid renderable for the docs page

* change phrasing in example assets slightly

* Apply suggestions from code review

Co-authored-by: Ylva Selling <ylva.selling@gmail.com>

* Remove labels support for `RenderableBoxGrid`

---------

Co-authored-by: Ylva Selling <ylva.selling@gmail.com>

data/assets/examples/renderable/renderableboxgrid/boxgrid.asset

@@ -0,0 +1,31 @@
+-- Basic
+-- This example adds a box grid, which is a 3D box rendered using grid lines, to the
+-- scene.
+--
+-- Per default, the box will be given a size of 1x1x1 meters, and here it is scaled up by a
+-- factor of 100. It will hence have a size of 100x100x100 meters.
+
+local Node = {
+  Identifier = "RenderableBoxGrid_Example",
+  Transform = {
+    Scale = {
+      Type = "StaticScale",
+      Scale = 100
+    }
+  },
+  Renderable = {
+    Type = "RenderableBoxGrid"
+  },
+  GUI = {
+    Name = "RenderableBoxGrid - Basic",
+    Path = "/Examples"
+  }
+}
+
+asset.onInitialize(function()
+  openspace.addSceneGraphNode(Node)
+end)
+
+asset.onDeinitialize(function()
+  openspace.removeSceneGraphNode(Node)
+end)

data/assets/examples/renderable/renderableboxgrid/boxgrid_size.asset

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+-- With Non-uniform Size
+-- This example creates a box grid with a non-uniform size. The size has been set so the
+-- box is two times larger in the Y-direction.
+--
+-- The `Size` values are given in meters, and here the box is scaled up by a factor of
+-- 100. So, the box will have a size of 100 times the `Size` values.
+
+local Node = {
+  Identifier = "RenderableBoxGrid_Example_Size",
+  Transform = {
+    Scale = {
+      Type = "StaticScale",
+      Scale = 100
+    }
+  },
+  Renderable = {
+    Type = "RenderableBoxGrid",
+    Size = { 1.0, 2.0, 1.0 }
+  },
+  GUI = {
+    Name = "RenderableBoxGrid - Non-uniform Size",
+    Path = "/Examples"
+  }
+}
+
+asset.onInitialize(function()
+  openspace.addSceneGraphNode(Node)
+end)
+
+asset.onDeinitialize(function()
+  openspace.removeSceneGraphNode(Node)
+end)

data/assets/examples/renderable/renderableboxgrid/boxgrid_styled.asset

@@ -0,0 +1,24 @@
+-- Styled
+-- This example creates a box grid where the grid lines are styled to have a specific
+-- color and line width.
+
+local Node = {
+  Identifier = "RenderableBoxGrid_Example_Styled",
+  Renderable = {
+    Type = "RenderableBoxGrid",
+    LineWidth = 4.0,
+    Color = { 1.0, 1.0, 0.0 }
+  },
+  GUI = {
+    Name = "RenderableBoxGrid - Styled",
+    Path = "/Examples"
+  }
+}
+
+asset.onInitialize(function()
+  openspace.addSceneGraphNode(Node)
+end)
+
+asset.onDeinitialize(function()
+  openspace.removeSceneGraphNode(Node)
+end)