Transition SamplePartition IDs to new format (fixes #571)

The IDs are dependent on SampleType (AR) id, so hardcode "P" for partition segment.

Sample: BRG-000?
AR: BRG-000?-R?
Partition: BRG-000?-P?
AR Templates - better sample partition handling

Templates still use part-? for their partitions,
this is just for the template markers, these are
not the sample partition IDs.