Add support for Organisation

[lasconic]

With the introduction of family mode and soon the holding/enterprise feature, Finary changed all the calls in the webUI and probably the app (I didn't test) from /users/me/XXX to organisations/<organisation_id>/XXX. We would need a nice way to handle that in the API wrapper and on the command line. So far /users/me/XXXis not deprecated but Finary could decide to remove it anytime

The not nice solutions I can think of :

• Adding --org-id as an option for all the command. Command line user will call finary_uapi organisations to get org id and then call the functions they want...
• For each user_ functions do a call a first call to users/me/organizations to get the main org and do the call with its id. (not nice because we can't get the results for other orgs)

A first step:

• implement a function to call users/me/organizations  #131