Update Gantt chart to be compatible with stages of the same type

[DanielRyanSmith]

The new schema allows for multiple stages of the same type (origin trial, shipping, etc.). The Gantt chart currently only reads from milestones of the first stage of each type, and ignores any information in other stages of that same type. Update the Gantt chart to read all relevant stages and display rows for multiples of the same stage type if relevant milestone information is available.