Implement Price Change Analysis Report

[jniles]

At the moment, BHIMA does not restrict users from changing prices of inventory items sold. This was born out of necessity, as often the prices are not well defined when BHIMA is installed. However, this is a problem for an institution that wants to enact strict pricing. The ability to lock price changes was proposed in #2174.

One way to get feedback on the pricing is to make a report that looks at what prices different users have set inventory items. Since BHIMA stores both the transaction price (the amount charged) and the inventory_price (the list price), this analysis is trivial. I've uploaded a sample pricing analysis that illustrates how to do this.

pricing_analysis.sql.txt

According to our clients, this report is quite useful. It would be be ideal if BHIMA could produce this style of report from our reports route. The BHIMA implementation does not have to use so many temporary tables (in fact, it probably shouldn't), but it should be able to produce a heatmap showing the inventory items that have been altered such as shown below:

User	TFA8.02	TF01+2 Polyclinique	TFP8.01 (Pediatrie)	TF5.35	TF5.01	TFA8.01	TFP3.02	TF4.04	TF5.36	TFA7.01	TFP5.28	TF4.21
Jeremie Mafinga	0	3	0	2	2	1	0	0	0	0	0	4
MOSENGO MANWANA Laurent	0	0	11	0	1	0	2	0	0	1	0	0
Mungongo koyi hyppolite	0	38	1	0	9	1	1	2	1	0	1	21
Nsimba-Mzusi Lydie	7	0	0	0	0	0	0	0	0	0	0	0
Nsukha Yoan	0	0	1	0	1	0	0	0	0	0	0	0
SAINT NZANZA	0	1	31	0	12	4	0	0	0	4	0	1