[IMP] portal: portal as a Directive

Before this commit, portal was a Component, now is a directive.
This commit also clean some unused code, and fix an issue on the clean
optimization when a portal is found in a condition or a loop.

src/app/template_helpers.ts

@@ -2,6 +2,7 @@ import { BDom, multi, text, toggler } from "../blockdom";
 import { validateProps } from "../component/props_validation";
 import { Markup } from "../utils";
 import { html } from "../blockdom/index";
+import { VPortal } from "../portal";
 
 /**
  * This file contains utility functions that will be injected in each template,
@@ -12,6 +13,16 @@ function withDefault(value: any, defaultValue: any): any {
   return value === undefined || value === null || value === false ? defaultValue : value;
 }
 
+function callPortal(
+  ctx: any,
+  parent: any,
+  key: string,
+  target: string,
+  content: (ctx: any, node: any, key: string) => BDom
+): BDom {
+  return new VPortal(target, content(ctx, parent, key)) as any;
+}
+
 function callSlot(
   ctx: any,
   parent: any,
@@ -186,6 +197,7 @@ export const UTILS = {
   zero: Symbol("zero"),
   isBoundary,
   callSlot,
+  callPortal,
   capture,
   withKey,
   prepareList,