update visual observations docs (#2787)

* update visual obs docs in Design Agents

* update screenshots with personal editor skin

docs/Getting-Started-with-Balance-Ball.md

 * **Behavior Parameters** — Every Agent must have a Behavior. The Behavior
   determines how an Agent makes decisions. More on Behavior Parameters in
   the next section.
-* **Visual Observations** — Defines any Camera objects used by the Agent to
-  observe its environment. 3D Balance Ball does not use camera observations.
 * **Max Step** — Defines how many simulation steps can occur before the Agent
   decides it is done. In 3D Balance Ball, an Agent restarts after 5000 steps.
 * **Reset On Done** — Defines whether an Agent starts over when it is finished.

docs/Learning-Environment-Design-Agents.md

 succeed at all.
 
 Visual observations can be derived from Cameras or RenderTextures within your scene.
-To add a visual observation to an Agent, either click on the `Add Camera` or
-`Add RenderTexture` button in the Agent inspector. Then drag the camera or
+To add a visual observation to an Agent, add either a Camera Sensor Component
+or RenderTextures Sensor Component to the Agent. Then drag the camera or
-of both attached to an Agent.
+of both attached to an Agent. For each visual observation, set the width and height
+of the image (in pixels) and whether or not the observation is color or grayscale.
 
 ![Agent Camera](images/visual-observation.png)
 
 
-In addition, make sure that the Agent's Policy expects a visual observation. In
-the Agent inspector, under **Behavior Parameters** > **Visual Observations**,
-specify the number of Resolutions the Agent is using for its visual observations.
-For each visual observation, set the width and height of the image (in pixels)
-and whether or not the observation is color or grayscale (when `Black And White`
-is checked).
-
-For instance, if you are using two cameras and one render texture on your Agent,
-three **Visual Observations** have to be added to the **Behavior Parameters**.
-During runtime, if a combination of `Cameras` and `RenderTextures` is used, all
-cameras are captured first, then all render textures will be added, in the
-order they appear in the editor.
-
-![Agent Camera and RenderTexture combination](images/visual-observation-combination.png)
-
-RenderTexture observations will throw an `Exception` if the width/height doesn't
-match the resolution specified under **Behavior Parameters** > **Visual Observations**.
+Each Agent that uses the same Policy must have the same number of visual observations,
+and they must all have the same resolutions (including whether or not they are grayscale).
+Additionally, each Sensor Component on an Agent must have a unique name so that they can
+be sorted deterministically (the name must be unique for that Agent, but multiple Agents can
+have a Sensor Component with the same name).
 
 When using `RenderTexture` visual observations, a handy feature for debugging is
 adding a `Canvas`, then adding a `Raw Image` with it's texture set to the Agent's
 
 ## Agent Properties
 
-![Agent Inspector](images/agent.png)
+![Agent Inspector](images/3dball_learning_brain.png)
 
 * `Behavior Parameters` - The parameters dictating what Policy the Agent will
 receive.
       be stacked and used collectively for decision making. This results in the
       effective size of the vector observation being passed to the Policy being:
       _Space Size_ x _Stacked Vectors_.
-  * `Visual Observations` - Describes height, width, and whether to grayscale
-    visual observations for the Policy.
   * `Vector Action`
     * `Space Type` - Corresponds to whether action vector contains a single
       integer (Discrete) or a series of real-valued floats (Continuous).
   * `Inference Device` - Whether to use CPU or GPU to run the model during inference
   * `Use Heuristic` - If checked, the Agent will use its 'Heuristic()' method for
   decisions.
-* `Visual Observations` - A list of `Cameras` or `RenderTextures` which will
-  be used to generate observations.
 * `Max Step` - The per-agent maximum number of steps. Once this number is
   reached, the Agent will be reset if `Reset On Done` is checked.
 * `Reset On Done` - Whether the Agent's `AgentReset()` function should be called