Improve documention font sizes and images

[Nicklas Nordborg]

For some reason the docbook-generated documentation seems to have a very large font. It's ok when viewing on a web page, but not so good when printing. Another issue is that several images are overflowing the page width. I can't recall that this happened before, so I'll see if we can do something clever with the css for the documentation to make it better.

[Nicklas Nordborg]

(In [6809]) References #1931: Improve documention font sizes and images

Changed to a 11pt as default font size and use relative fonts in all other places.

Images can now only be max 100% wide when printing.

[Nicklas Nordborg]

(In [6810]) References #1931: Improve documention font sizes and images

Make screenshots a bit smaller when printing.

Set fixed width on screen.