With these changes, we allow the contract line start date to be computed
using the order confirmation date. When the product is configured with
any of the options set in contract_start_date_method other than manual,
the start date will be calculated based on the established date and the
selected period.
Additionally, we can force the month in which we will work in case the
frequency is yearly, quarterly, or semesterly.
Is not added support for daily, weekly or monthlylastday in this commit.
Before this changes, when trying to edit a line of sale order, it was
opening the form of the line. But following the way to work of odoo
with sale event, we have make a new contract configurator that will
be opened when selecting a product of type contract.
