Standardise bi/mbbi names

Currently we have no standard on the names of mbbi/bi values, specifically lower/upper case. We should:

* Write a standard (and put it on the wiki)
* Ensure all bi/mbbis are meeting said standard
* Add a check in somewhere like the PVUnitsChecker script (maybe rename this)

Start by locating the PVUnitsChecker script and reviewing the existing bi/mbbi values to identify current casing patterns. Define the naming standard on the wiki, bring all bi/mbbi values into compliance, and update or rename the checker so it detects violations. Done means the standard is documented and the checker passes against the full set of values.

Scritto dal modello di indicizzazione a partire dal testo della issue.