Add  in your xml

From footer:

<template id="remove_footer" inherit_id="web.menu_secondary">

    <xpath expr="//div[2]" position="replace">

        <!--<div class="oe_footer">-->

            <!--Powered by <a href="http://www.odoo.com" target="_blank"><span>Odoo</span></a>-->

         <!--</div>-->

    </xpath>

</template>

You could follow this guide

http://odoo.guide/debranding-odoo-backend/

or buy one of this modules that do that

https://www.odoo.com/apps/modules/9.0/web_debranding/

http://odooshoppe.com/shop/product/odoo-debranding-16

Also this free app is for debrand Odoo mails

https://apps.openerp.com/apps/modules/8.0/mail_debrand/