Recipient org type chart double counting grants

[mariongalley]

The problem:

The Recipient Org Type chart in GrantVis is showing the same grants across multiple bars when a Recipient is known to have several types of identifier.

While it is technically accurate than an org can be e.g. both a charity and a company at the same time, this is an issue in GrantVis because:

1. all the other charts allocate each grant to a single bar/area. We don't model 1-many relationships for any of the other fields (like location). It's confusing/unexpected for users for this chart to be the only one that double counts grants.
2. the majority of users want to know information about org types because it is useful (and will soon become required for reporting to the Charity Commission) to know how many non-charitable companies were funded by charitable grantmakers. GrantVis is able to provide grantmakers with genuine insights into their own data that they may not be able to get themselves, so we should ensure it meets their needs.

The proposed solution:

For each recipient, we should assign a 'canonical' org type, in the same way we assign a canonical name and identifier. This should give precedence to charity number (in line with existing logic for ids)