Energy stuff with reset

[Christian-B]

Makes changes to allow energy reports over multiple runs and reset

1. Adds a mapping from n_run to n_reset in global_provenance.sqlite3

• With extra views to access the provenance data by reset

3. Compute Energy Gets the timer data just for this reset
4. Virtual power cores come from placements and not the database
5. ProvenanceReader.get_last_run_database_path removed as it as wrong! And not needed
6. power_provenance now by run
7. energy report per run (CUMULATIVE per reset!)

Fixes: #866

tested by:
SpiNNakerManchester/sPyNNaker#1513 (needs to be merged too)