reveal-title-slide-template should allow multiple values and concat them

[VladimirAlexiev]

I have found it very useful to specify several #+REVEAL_TITLE_SLIDE_TEMPLATE: lines, and have them concatenated (see org-export-options-alist):

    (:reveal-title-slide-template "REVEAL_TITLE_SLIDE_TEMPLATE" nil org-reveal-title-slide-template space)

(Since this is HTML, it doesn't matter whether the separatr is space or newline)

For example, I have this bunch of lines, which make the extra links in this presentation:

#+REVEAL_TITLE_SLIDE_TEMPLATE: <h2>%t</h2><h3>%e</h3><h3>SmartCulture Conference</h3><h3>%d, Brussels</h3>
#+REVEAL_TITLE_SLIDE_TEMPLATE: <p/><p/><p class='center'>
#+REVEAL_TITLE_SLIDE_TEMPLATE: <a href='http://VladimirAlexiev.github.io/pres/20140611-SmartCulture-sem-tech-CH/index.html' target='_blank'>2D interactive version</a>,
#+REVEAL_TITLE_SLIDE_TEMPLATE: <a href='http://VladimirAlexiev.github.io/pres/20140611-SmartCulture-sem-tech-CH/Semantic Technologies for Cultural Heritage.pdf'>pdf</a>,
#+REVEAL_TITLE_SLIDE_TEMPLATE: <a href='http://www.slideshare.net/valexiev1/semantic-technologies-for-cultural-heritage-35749530' target='_blank'>slideshare</a>.
#+REVEAL_TITLE_SLIDE_TEMPLATE: Press <a href='javascript:Reveal.toggleOverview()'>O for overview</a>,
#+REVEAL_TITLE_SLIDE_TEMPLATE: <a href='reveal-help.html' target='_blank'>H for help</a>.</p>
#+REVEAL_TITLE_SLIDE_TEMPLATE: <p class='center'>
#+REVEAL_TITLE_SLIDE_TEMPLATE: Proudly made in plain text with 
#+REVEAL_TITLE_SLIDE_TEMPLATE: <a href='https://github.com/hakimel/reveal.js/'>reveal.js</a>, 
#+REVEAL_TITLE_SLIDE_TEMPLATE: <a href='https://github.com/yjwen/org-reveal'>org-reveal</a>, 
#+REVEAL_TITLE_SLIDE_TEMPLATE: <a href='http://orgmode.org'>org-mode</a> and 
#+REVEAL_TITLE_SLIDE_TEMPLATE: <a href='http://www.gnu.org/s/emacs/'>emacs</a>.</p>

You might even consider some variation of this for the default value

[yjwen]

Thanks for the suggestion. Just changed as you suggested. :)