[IMP] component: components key is now static

This is a breaking change!

closes #279

src/component/component.ts

@@ -92,6 +92,7 @@ export class Component<T extends Env, Props extends {}, State extends {}> {
   get el(): HTMLElement | null {
     return this.__owl__.vnode ? (<any>this).__owl__.vnode.elm : null;
   }
+  static components = {};
 
   env: T;
   state?: State;

src/component/directive.ts

@@ -388,7 +388,7 @@ QWeb.addDirective({
     // new component
     ctx.addLine(`let componentKey${componentID} = ${ctx.interpolate(value)};`);
     ctx.addLine(
-      `let W${componentID} = context.components && context.components[componentKey${componentID}] || QWeb.components[componentKey${componentID}];`
+      `let W${componentID} = context.constructor.components[componentKey${componentID}] || QWeb.components[componentKey${componentID}];`
     );
     // maybe only do this in dev mode...
     ctx.addLine(