small fixes

Corrected some typos. Added auto start slideshow for photoswipe. Changed
the social links so that they open in a new tab.
Baktun13

Added the framework for Baktun-13. Added a screenshot and thumb.
Description still needed.
Baktun13 details

Added more details to the Baktun 13 entry and fixed the position of the
gallery and all additional ones should clear: both