VersionAlert for Unity

Added new icons for Spline UI elements.
Modified knot handles so they are hidden if the `EditorTool` is not a `SplineTool`.

[1403386] Fixing SplineData Inspector triggering to SplineData.changed events.
[1403359] Fixed issue where `SplineExtrude` component would not update mesh after an undo operation.
Fixed `SplineUtility.Evaluate` not evaluating the up vector correctly.
Fixed InvalidOperationException thrown when Spline is created with a locked Inspector.
[1384448] Fixed incorrect Rect Selection when using Shift or CTRL/CMD modifiers.
[1384457] Fixed an issue where an exception was thrown when drawing a spline and rotating the scene view.

com.unity.splines 1.0.1