Explicitly flag if portfolio should be checked in calc_wieghts prechecks

[AlexAxthelm]

          Ah, yeah I see the point.

I guess the flag should really indicate something along the lines of "should I expect output files from the audit process to have been created already?"

So maybe something along the lines of:

  analysis_prechecks(
    total_portfolio_path = NULL,
    pacta_data_dir = pacta_data_dir,
    output_dir = output_dir,
    check_audit_outputs = TRUE
  )

and in run_pacta it would be:

  analysis_prechecks(
   ...,
    check_audit_outputs = FALSE
  )

Originally posted by @jdhoffa in #83 (comment)

[AlexAxthelm]

Closed via #88