Use scaled down jpg for backgrounds

Down from 6.6MB to 738 KB, to avoid huge PDF files for resulting slides.

Converted from PNG to JPG (as it's mostly a photo) and resized from 2880x1618 to
1920x1080.

Update README.md

See merge request urs.baumann/ost-beamer-theme!1

Use \selectlanguage{german} befor \usetheme{ost} for the german background

Ensure that footnotes are visible

Remove lstMakeShortInline

Doing this:

    \documentclass{beamer}
    \usetheme{ost}
    \usepackage{standalone}
    \begin{document}
    \end{document}

Fails with

    (/usr/share/texmf-dist/tex/latex/standalone/standalone.sty
    (/usr/share/texmf-dist/tex/latex/tools/shellesc.sty)
    (/usr/share/texmf-dist/tex/latex/xkeyval/xkeyval.sty
    (/usr/share/texmf-dist/tex/generic/xkeyval/xkeyval.tex
    (/usr/share/texmf-dist/tex/generic/xkeyval/xkvutils.tex)))
    ! Missing \endcsname inserted.
    <to be read again>
    \let
    l.193 \@namedef{sa@mode@image|tex}
                                    {%
    ?

Similarly, when the pgf/TikZ is used, it fails with:

    (/usr/share/texmf-dist/tex/generic/pgf/libraries/pgflibraryplothandlers.code.tex)
    ! Missing \endcsname inserted.
    <to be read again>
    \let
    l.1198 ...earrow{name=|<->|,   means={>[sep=0pt].|}}
                                                      %
    ?

It seems like a really bad idea to redefine a character which is used
internally in probably dozens of LaTeX internals to do something
entirely different. It seems like an even worse idea to do this as part
of a theme which doesn't even use that shorthand ;-)

Rename internal \centerbox to avoid conflict

When the adjustbox package is used, this theme fails with:

    ! LaTeX Error: Command \centerbox already defined.
                   Or name \end... illegal, see p.192 of the manual.

    See the LaTeX manual or LaTeX Companion for explanation.
    Type  H <return>  for immediate help.
     ...

    l.64 \newcommand\centerbox[1]{$\vcenter{\hbox{#1}}$}

Since `\centerbox` is only used internally, it should have a matching
name, see e.g. https://tex.stackexchange.com/a/8353/28697 as well as
http://texdoc.net/texmf-dist/doc/latex/dtxtut/dtxtut.pdf
(end of page 21).

Template fix for figures

Markdown/Pandoc Beispiel