Remove ageing out transitions from placement starts graph

[MichaelHanksSF]

Currently, the placement starts graph counts every placement start. However, we've added some artificial starts that are based on the child ageing into the next age bracket, as this is easier for modelling transitions.

These need to be removed. I think the easiest way to do this will be by:

• amending the logic that creates these placements (in datacontainer) to label the RNE as "A" (for age) or something similar
• filter RNE = "A" placements out when plotting historic starts