fix broken links and missing devguide (#566)

Author: vkovec

com.unity.formats.fbx/Documentation~/devguide.md renamed to com.unity.formats.fbx/Documentation~/api_index.md

@@ -64,7 +64,7 @@ To manually install an Autodesk® Maya® or Autodesk® Maya LT™ Integration:
    `UnityFbxForMaya {Version} {UnityIntegrationsPath}/Integrations/Autodesk/maya`
 
    **Note:** You need to replace:
-   * `{Version}` by the version number of your FBX Exporter package (for example, `2.0.0`)
+   * `{Version}` by the version number of your FBX Exporter package (for example, `4.0.0`)
    * `{UnityIntegrationsPath}` by the location where you unzipped `UnityFbxForMaya.zip` in first step.
    <br />
 

com.unity.formats.fbx/Documentation~/images/FBXExporter_RunComponentUpdater.png

@@ -2,7 +2,7 @@
 
 In Unity, [Nested Prefabs](https://docs.unity3d.com/Documentation/Manual/NestedPrefabs.html) allow you to create Prefabs inside other Prefabs, and [Prefab Variants](https://docs.unity3d.com/Documentation/Manual/PrefabVariants.html) allow you to save a variation on an existing Prefab.
 
-When Unity imports a Model from a 3D modeling application such as Autodesk® Maya®, Unity creates a **Model Prefab**, which is a read-only representation of the FBX file's contents. You can't edit Model Prefabs in Unity, apart from [changing the import settings](https://docs.unity3d.com/2018.3/Documentation/Manual/class-FBXImporter.html). When the FBX file is modified inside the originating 3D modeling software, Unity updates the Model Prefab.
+When Unity imports a Model from a 3D modeling application such as Autodesk® Maya®, Unity creates a **Model Prefab**, which is a read-only representation of the FBX file's contents. You can't edit Model Prefabs in Unity, apart from [changing the import settings](https://docs.unity3d.com/Documentation/Manual/class-FBXImporter.html). When the FBX file is modified inside the originating 3D modeling software, Unity updates the Model Prefab.
 
 ![A Model Prefab in the Scene and Hierarchy views](images/FBXExporter_ModelPrefab.png)
 

com.unity.formats.fbx/Documentation~/integration.md

@@ -19,7 +19,7 @@ With the FBX Exporter and the [Unity Recorder](https://docs.unity3d.com/Packages
 
 4. Select **Start Recording**.
 
-> **Note:** Alternatively, you can use the FBX Recorder through a [Recorder Clip](https://docs.unity3d.com/Packages/com.unity.recorder@latest/RecordingTimelineTrack.md) in a [Timeline](https://docs.unity3d.com/Packages/com.unity.timeline@latest) track.
+> **Note:** Alternatively, you can use the FBX Recorder through a [Recorder Clip](https://docs.unity3d.com/Packages/com.unity.recorder@latest) in a [Timeline](https://docs.unity3d.com/Packages/com.unity.timeline@latest) track.
 
 ## FBX Recorder properties
 

com.unity.formats.fbx/Documentation~/prefabs.md

@@ -70,7 +70,7 @@ To avoid this, make sure to convert only the Tree when finished editing. Otherwi
 
 ## Trail and line particles lose Material after being converted
 
-If you lose Materials when converting trail or line particles, you need to re-apply the Materials to the FBX Linked Prefab after conversion.
+If you lose Materials when converting trail or line particles, you need to re-apply the Materials to the FBX Prefab Variant after conversion.