Improved event managment (and other minor changes)

Event management:
- Added event emitter class, to homogenize all events handling
- Added event emitter for Touch Events
- Added Time event, for events that are produced after a given time
- Added event emitter for Time event
- Updated tech demo to include these events
Other things:
- Added originX and originY to transformations

Wiki update related: https://github.com/e-ucm/ead/wiki/Behaviors