Add render_ee and override render_ce for views

Issue: #271

We have a CE layout file: app/views/layouts/_page.html.haml.

We want to reuse this layout file and extend it in JH folder:

jh/app/views/layouts/_page.html.haml

= render_ee("layouts/page")

ExtendedContent

How to use

In JiHu repo:

• If you want to extend the EE view, use render_ee;
• If you want to extend the CE view, and EE view does not exist, use render_ee;
• If you want to jump EE view and extend CE view, use render_ce;