feat(store): cut/copy/paste support

src/store/index.ts

@@ -10,6 +10,7 @@ import { Pattern } from './pattern';
 import { Project } from './project';
 
 export class Store {
+	@MobX.observable private clipboardElement?: PageElement | undefined;
 	@MobX.observable private currentPage?: Page;
 	@MobX.observable private patternSearchTerm: string = '';
 	@MobX.observable private projects: Project[] = [];
@@ -25,6 +26,10 @@ export class Store {
 		this.currentPage = undefined;
 	}
 
+	public getClipboardElement(): PageElement | undefined {
+		return this.clipboardElement;
+	}
+
 	public getCurrentPage(): Page | undefined {
 		return this.currentPage;
 	}
@@ -150,6 +155,10 @@ export class Store {
 		this.patternSearchTerm = patternSearchTerm;
 	}
 
+	public setClipboardElement(clipboardElement: PageElement): void {
+		this.clipboardElement = clipboardElement;
+	}
+
 	public setSelectedElement(selectedElement: PageElement): void {
 		this.selectedElement = selectedElement;
 	}

src/store/page/page_element.ts

@@ -58,6 +58,17 @@ export class PageElement {
 		child.setParent(this, index);
 	}
 
+	public clone(): PageElement {
+		const clone = new PageElement(this.pattern);
+		this.children.forEach(child => {
+			clone.addChild(child.clone());
+		});
+		this.propertyValues.forEach((value: PropertyValue, id: string) => {
+			clone.setPropertyValue(id, value);
+		});
+		return clone;
+	}
+
 	protected createChildElementOrValue(json: JsonValue, store: Store): PageElement | PropertyValue {
 		if (json && (json as JsonObject)['_type'] === 'pattern') {
 			return PageElement.fromJsonObject(json as JsonObject, store, this);