Pass through the calculated dimensions to the template

[ramonski]

Description of the issue/feature this PR addresses

This PR passes the calculated page/content dimensions through to the rendered template.
The values are available in the options dictionary from within a page template, e.g.:

<pre tal:content="options"/>

{'page_width': 210.0, 'name': 'DIN A4', 'format': 'A4', 'margin_right': 20.0, 'content_width': 170.0, 'margin_top': 10.0, 'margin_left': 20.0, 'content_height': 277.0, 'margin_bottom': 10.0, 'page_height': 297.0}

Current behavior before PR

The template had no knowledge about the calculated dimensions

Desired behavior after PR is merged

Calculated dimensions can be used in page templates

--
I confirm I have tested this PR thoroughly and coded it according to PEP8
and Plone's Python styleguide standards.