Building a labware component

Built component to display various types of labware using SVG.
Built component to dynamically display different types of labware.
Built a component that scans & displays labware.
Fixed up some event handlers that propogated their events.
Worked on composite event handlers, which isn't quite right.
Fixed up display of the SVG.
When no labware use the "unknown" labware for display.
Enable labelling to respond to the "focus" event.
Ensure that the labware scanning component handles "focus" events.
Pulled better code from presenter.js into standard_mappers.js.
Reuse standard mappers in the presenter code.
Use the labware display component in re-racking.