Add nodes_avail to the select_[g|p]_step_pick_nodes function to be able
to get from the plugin available nodes to run step on.

This is needed for a Cray when running with Network performance counters.
CRAY - Add logic to be able to store which blades are being used.
CRAY - add logic to be able to limit steps to 1 per blade if using network
performance counters.
CRAY - rename blades_running_* to better descriptive blade_nodes_running_*
CRAY - fix call to incorrect function
Better logic to get the select_nodes_avail bitmap to work correctly.
Remove this so I can test Cray code on a non-cray box
Set SELECT_JOBDATA_NETWORK on all systems.
update news about performance counters