simplify core-properties; add xsd comment

src/file/border/border.ts

@@ -24,8 +24,11 @@ import { eighthPointMeasureValue, hexColorValue, pointMeasureValue } from "../va
 
 export interface IBorderOptions {
     readonly style: BorderStyle;
+    /** Border color, in hex (eg 'FF00AA') */
     readonly color?: string;
+    /** Size of the border in 1/8 pt */
     readonly size?: number;
+    /** Spacing offset. Values are specified in pt */
     readonly space?: number;
 }