Feature: transfers between members of different organisations

[franpb14]

I will make the current "time transfer for this offer" button work even if it is an offer from another organisation. This will allow different organisations to exchange time with each other.

The button will work as follows when the exchange is between different organisations:
member A and his organisation give one hour and member B and his organisation get one hour. So now the sum of time of the members of organisation A will be -1 and of organisation B will be 1.

For this Issue the way to share an offer from another organisation will be via URL, then we will look at how to implement a search engine.

[sseerrggii]

I think is a good first step. Someday we can show only accountability between organizations, limits of credit between organitzacions or other rules for interbank exchanges

[sseerrggii]

Some specification in order to finish this feature:

• We need some view, can be public view, with balances between organizations
• We need to discuss how user can ask for service or pay a offer preserving users privacy (only users share their date inside their organization)

Configuration (Admins of organizations)

• Ability to choose if our organizations could trade with others
• Ability to ban some organizations (names or max balance interbanks, like we won't trade with organizations dat have more than 500h of debt)