'sub-account' or 'role' for truck leasing companies

[BenGardiner]

In #153 some possible ways to grant access to leasing companies of fleet data are considered.

Either we add a role and leasing companies get access to entirety of fleet vehicles or we recommend TSP (sub) accounts for leasing companies and the fleet vehicles they get access to are limited by what on that account.

How we handle #150 will influence how we should handle this issue.

[BenGardiner]

We are going to defer both roles and separate accounts for use by leasing companies into a later release. For now we will leave it up to TSPs to handle the multi-party relationship as they always have.

c.f. #164 (review)