Bug #3/ #1, Fix for student visualization link - "?embed=1"

* https://github.com/IET-OU/oer-evidence-hub-org/issues/3
Adding "update" command to GNU Makefile
Bug #17, Add custom variables to Google Analytics event tracking

* ...JuxtaLearn
* https://github.com/IET-OU/oer-evidence-hub-org/issues/17