Organisation should expose Class property

[emacinty]

The Accounting\Organisation model doesn't currently expose Class, which is documented here. This typically shows whether an Organisation is TRIAL, PREMIUM etc. This is relevant if, for example, you want to see if multiple currencies are supported (even if they don't at present exist in the organisation).

It was a relatively simple change to make locally; I've attached my diff which others may wish to use to apply whatever style is appropriate in the project.

diff.txt

[calcinai]

@emacinty feel free to submit a PR and I'll merge that one in, thanks!

[emacinty]

Thanks!

[calcinai]

No, thank you!