Clean app.js

[xavierfav]

In static/javascripts/app.js, interaction functionalities and sequencer scheduling are mixed together.
It would be nice, for clarity, to split these two different logics in different files.

For instance:

• app.js could only launch the initialization functions.
• sequencer.js could take care of the sequencer scheduling.
• controller.js could take care of the controls and user interactions.