libE_stats.txt should give sim_id for sim funcs instead of a count

[shuds13]

For sims, change Calc to sim_id.

• This should reflect the naming of output directories for sim_ids (should re-use code), and is more intuitive for users.
• Will need to check postprocessing scripts still work.
• Gens can still use sequential numbers - also mirroring output directories.
• As before the output will be right aligned at width 5, but will expand if required.

[jlnav]

Tentatively closed by #588 ?