GFR: Sort RG locations by volume of holdings

[jmfcoleman]

The order of locations for record groups is misleading and is likely to direct researchers to the wrong location. For example, a search for RG 233 returns several locations and the Center is towards the bottom of the list. It is not clear that the Center is the primary custodial unit for RG 233 and has the vast majority of holdings. Can we sort RG locations by volume of holdings?