separating sound enabling and sound customizing (might solve the no more sound issue)
adding field 'intro' in root of SequenceDescription and validation of it
adding intro field in sequence, and declare and populate intro layout in page
Merge branch 'develop' of https://github.com/daydreaming-experiment/app into feature/eurostar
layout improvements for page and questiosn
Merge pull request #199 from daydreaming-experiment/feature/eurostar

Feature/eurostar