[FIX] planner: less gready with reflow and better integration with webclient (oe_systray)

* Only trigger a menu reflow when needed (show/hide planner)
* Do not include webclient and menu; use webclient reference
(Courtesy of sle-odoo)

Also, change the way to switch planner page. Switching keep now the URL fragment of the webclient, and don't use collapse bootstrap class. Fix url builder server side.