A Subscription Request is a ticket, which should be used to generate an Open Sale Order for a service.
When the Open Order is created, the ticket is closed, and not used anymore.

Drop the Subscription Condition object.
Using Sale Trade Condition is enough to define all the Open Order profiles.
Using Sale Supply is enough to define the prices.

As services can be created from SlapOS API, the Subscription Request
can be created after the service already exists.
Block allocation until the Open Sale Order has not been yet created.
User will be able to fill the services details, without it being used in the system.

Open Sale Order must be created, even if the service is free, to allow
using the inventory API on the services (using Packing List).

In order to reduce the number of invoice for the customer, ensure the
invoice date is stable for a customer, and provide discount to not invoice
unused period.
Do not use the same date for every users, to reduce load on the system
for that day.

To accept a payable service Subscription Request, the customer must
provide a deposit, which may be used to pay a not paid monthly invoice.

Also in this commit:
* drop not needed templates
* use interaction workflow to trigger alarms
* drop ecommerce dependency