[doc] Elaborated site view structure
core.addMediaToWork + minor fixes.
Check original work permissions when linking media.
Misc fixes.
Merge pull request #40 from commonsmachinery/core-media

Core media
Merge remote-tracking branch 'origin/master' into log-events

Conflicts:
	doc/datamodel/event.md
	modules/core/lib/work.js
	modules/core/tests/test_media.js