Restrict standout font and alignment to inner content

Restore theme within frame, making standout slides work with ignorenonframetext

So that the speaker's notes aren't affected by the typesetting of the slide.

Restore theme within frame, making standout slides work with ignorenonframetext

Update URL to Paul Tol technical note

The BSD /bin/echo doesn't know the option '-e'

This ensures that the whole text of a footnote has the same indentation
and not just the line following the footnote mark

The upper part of the slide is white text on dark background.
For the title graphic part it's the other way round, so switch
the text color back to black.

Updated Fira font paths

Fixed docker build command in Makefile.

Patch latest beamer section commands

This fixes #303.