Rename references to account_id/accountId to account_number

[croissanne]

In CRC org_id is used to refer to a number that organization admins have access to really. And account_number is the shared number over an organization.

So let's rename account_id/accountId references to account_number (but keep org_id as is). To keep it consistent and avoid future confusion. Migrate the db as well, since we currently have a single table without any references to account_id, we can just rename it to account_number.

[croissanne]

As a note: the personal/individual number is identity["user_id"]; this should be unique across an organization. When we want to track composes of individual numbers as well we might need to use org_id + user_id combo.