added SITE_* settings
use SITE_HOME to set the home page
added context processor to make site settings available in templates
fixing #327, adicionando checagem de existencia de video antes do play. Resolve pra qualquer caso.
Merge pull request #328 from mupi/timtec/issue327

add check for existing video before playing, fixes #327
Merge pull request #319 from barraponto/site_abstract

abstracting TIMTec details
fix lesson slug conflict, fixes #331
Merge branch 'issue331'
fix pipeline js confs and pep8 issues
Merge branch 'master' into professormessages

Conflicts:
	core/models.py