Implemented system process wrapper and avconv-based video converter.
Added missing files.
Merge branch 'master' into jcodec
Merge master into jcodec.
Merge branch 'jcodec'

Conflicts:
	structr-ui/src/main/resources/structr/js/entities.js
	structr-ui/src/main/resources/structr/js/websocket.js
Merge branch 'master' of github.com:/structr/structr