TRQ-2460. Add two new entries to the accounting file.

Add total_execution_slots and unique_node_count to the accounting file.
total_execution_slots is the total number of processors, whether
physical or logical, used by the job.
unique_node_count is the number of unique hosts the job used.

Conflicts:
	src/server/accounting.c
	src/server/test/accounting/test_accounting.c