Fix several tooltip issues

- https://github.cds.internal.unity3d.com/unity/vfx-graphics/pull/30#discussion_r89530
- https://github.cds.internal.unity3d.com/unity/vfx-graphics/pull/30#discussion_r89531
- https://github.cds.internal.unity3d.com/unity/vfx-graphics/pull/30#discussion_r89532
- https://github.cds.internal.unity3d.com/unity/vfx-graphics/pull/30#discussion_r89533
- https://github.cds.internal.unity3d.com/unity/vfx-graphics/pull/30#discussion_r89534
- https://github.cds.internal.unity3d.com/unity/vfx-graphics/pull/30#discussion_r89535
- https://github.cds.internal.unity3d.com/unity/vfx-graphics/pull/30#discussion_r89536
- https://github.cds.internal.unity3d.com/unity/vfx-graphics/pull/30#discussion_r89538
- https://github.cds.internal.unity3d.com/unity/vfx-graphics/pull/30#discussion_r89539
- https://github.cds.internal.unity3d.com/unity/vfx-graphics/pull/30#discussion_r89540
- https://github.cds.internal.unity3d.com/unity/vfx-graphics/pull/30#discussion_r89541
- https://github.cds.internal.unity3d.com/unity/vfx-graphics/pull/30#discussion_r89542
- https://github.cds.internal.unity3d.com/unity/vfx-graphics/pull/30#discussion_r89544
- https://github.cds.internal.unity3d.com/unity/vfx-graphics/pull/30#discussion_r89545
- https://github.cds.internal.unity3d.com/unity/vfx-graphics/pull/30#discussion_r89546
- https://github.cds.internal.unity3d.com/unity/vfx-graphics/pull/30#discussion_r89547
- https://github.cds.internal.unity3d.com/unity/vfx-graphics/pull/30#discussion_r89548
- https://github.cds.internal.unity3d.com/unity/vfx-graphics/pull/30#discussion_r89549
- https://github.cds.internal.unity3d.com/unity/vfx-graphics/pull/30#discussion_r89550

Author: PaulDemeulenaere

com.unity.visualeffectgraph/Editor/Models/Blocks/Implementations/Position/PositionMesh.cs

@@ -27,7 +27,7 @@ class PositionMesh : PositionBase
         [VFXSetting, SerializeField, Tooltip("Specifies how Unity handles the sample when the custom vertex index is out the out of bounds of the vertex array.")]
         private VFXOperatorUtility.SequentialAddressingMode mode = VFXOperatorUtility.SequentialAddressingMode.Clamp;
 
-        [VFXSetting, SerializeField, Tooltip("Change what kind of primitive we want to sample.")]
+        [VFXSetting, SerializeField, Tooltip("Specifies which primitive part of the mesh to sample from.")]
         private SampleMesh.PlacementMode placementMode = SampleMesh.PlacementMode.Vertex;
 
         [VFXSetting, SerializeField, Tooltip("Surface sampling coordinate.")]

com.unity.visualeffectgraph/Editor/Models/Operators/Implementations/SampleMesh.cs

@@ -125,7 +125,7 @@ public enum SourceType
         [VFXSetting, SerializeField, Tooltip("Specifies how Unity handles the sample when the custom vertex index is out the out of bounds of the vertex array.")]
         private VFXOperatorUtility.SequentialAddressingMode mode = VFXOperatorUtility.SequentialAddressingMode.Clamp;
 
-        [VFXSetting, SerializeField, Tooltip("Change what kind of primitive we want to sample.")]
+        [VFXSetting, SerializeField, Tooltip("Specifies which primitive part of the mesh to sample from.")]
         private PlacementMode placementMode = PlacementMode.Vertex;
 
         [VFXSetting, SerializeField, Tooltip("Surface sampling coordinate.")]