Added delete query option.

Also, previous commit included refactoring of bus deletion (for buses
that have departed), and fix of the chart.timer (typo with chart.time).
WIP - displays time of selected arc on SVG.

However, have issue with the revert action ("unclicking" a selection).
Somehow, a closure is being created with the .on('click') handler and
it is referencing dataset from the first initialization.
Fixed "unclick" issue by moving event handler away from enter().