[Hart] CSS fixes

* header/footer spacing tweaks
* header centered, even on mappage
    by taking out of .container and into .header-container
* push .skipped-map downwards
    fixes mysociety/FixMyStreet-Commercial#486 on Safari and IE
* header/footer width tweaks
    width (instead of max-width) was making page overflow, causing
    artefacts in footer.  Also the mobile-nav was visible on desktop, to
    the far right.
* remove link hover from images
* fix inconsistent header height
* more spacing on .mappage .content

From https://github.com/mysociety/FixMyStreet-Commercial/issues/487
[Hart] avoid the word "problems" on front page

From https://github.com/mysociety/FixMyStreet-Commercial/issues/487
[Hart] correct links for FAQ

From https://github.com/mysociety/FixMyStreet-Commercial/issues/487
[Hart] footer links corrected
[Hart] css push report sidebar comments down

Fixes https://github.com/mysociety/FixMyStreet-Commercial/issues/488