Cleanup: Move asset mixins to includes/mixins

We use a separate file for mixins to make views more readable. LP#15202477
Add full screen categories menu

Append menu on the right side of the screen. It overtakes all screen focus qua an overlay on the toggle element (may be moved to another).

Also appends natmus.js to allow for jQuery.

LP#15202477
Initial setup of Category menu

Get ready to show submenus in category menu. Probably requires some kind of Angular $watch in app.js.

Also style adjustments for toggle icon.

LP#15202477
Change header, remove container padding and adjust font size

The task is broad aimed at frontend issues with the new Natmus site. This commit contains a new header with logo and logotype. We also add svg menu icon with "open" color.

To use more space on mobile, we remove container class padding. This may have implications on later use, but it's the best way to achieve the wanted look.

Font base size has been decreased. Some headings also need a .hx class to be even smaller.

Tables have been styled in a run-in style. This is not completed yet, because some fields demand special handling.

LP#15202477 and LP#15771745
Adjust header to desktop view

There is a new desktop mockup, which requires some changes in markup and classes (cf. LP#15771745).

The tricky part is to change rendering order of logos area and search/menu area. We use Bootstrap rows and cols to do it. But we have to set menu parent rows to display static - otherwise we can't overlay the screen "on menu open". If this creates cross browser/device problems, we may use another element for overlay.

LP#15771745 and LP#15202477
Merge pull request #19 from NationalMuseumofDenmark/FrontendDesign#15202477

Frontend design#15202477
Merge pull request #20 from NationalMuseumofDenmark/master

Update testing with frontend changes