Add report on % stock outs by depot

[jniles]

Here is an analysis I did of some data recently:

It would be nice to have this style of report come directly out of BHIMA. It uses the RUMER report to aggregate totals, and determine the % of stock out by pharmacy.

The way this is calculated is as follows:

1. For each medication, determine the number of days it would be available in the pharmacy (if the period is N days, this is N).
2. The total number of medication-days is the total number of medications * the total number of days they might be available.
3. The total number of days of stock out are the total number of days the quantity in stock was 0 for any medication.

[jniles]

The colors above represent my own personal analysis, but it might be good to color the ratios like we do for the "Recovery Capacity Report".