[FIX] Allow registrars to access/modify registrant
[IMP] Added Pagedown Editor and Previewer to abstract submission
[IMP] Added Markdown and MathJax integration to abstract submission, editing and viewing
[IMP] Pagedown and MathJax in external modules

 * Also included proper assets in headers
[IMP] Better looking preview
[FIX] Added the remaining Markdown editing and rendering in abstracts and contributions, cleaned some code
[IMP] First work on LaTeX PDF generation, not finished and still buggy
[IMP] LaTeX PDF generation on Abstracts and Contributions
[IMP] LaTeX PDF generation on User Abstracts Book
[IMP] LaTeX PDF generation on Contributions Book (on event page) and Abstracts compilation (in event management area)
[IMP] LaTeX PDF generation on Contributions compilation (in event management area)
[IMP] Added class to handle the all the PDF generation from LaTeX, organized LaTeX templates in specific files, some code cleaning
[MIN] Minor fixes in LatexRunner() and templates
[IMP] Added logging to PDF LaTeX generation results
[IMP] Changed LaTeX templates rendering to Mako
[FIX] Post-rebase fixes
[FIX] Missing render() import and PEP8 stuff
[FIX] Some more display fixes