Desktop: Simplified and improve command service, and added command palette

- Commands "enabled" state is now expressed using a "when-clause" like in VSCode
- A command palette has been added to the Tools menu

ReactNativeClient/lib/commands/historyForward.ts

@@ -7,23 +7,13 @@ export const declaration:CommandDeclaration = {
 	iconName: 'icon-forward',
 };
 
-interface Props {
-	hasForwardNotes: boolean,
-}
-
 export const runtime = ():CommandRuntime => {
 	return {
-		execute: async (props:Props) => {
-			if (!props.hasForwardNotes) return;
+		execute: async () => {
 			utils.store.dispatch({
 				type: 'HISTORY_FORWARD',
 			});
 		},
-		isEnabled: (props:Props) => {
-			return props.hasForwardNotes;
-		},
-		mapStateToProps: (state:any) => {
-			return { hasForwardNotes: state.forwardHistoryNotes.length > 0 };
-		},
+		enabledCondition: 'historyhasForwardNotes',
 	};
 };