[IMP] product_contract: Add contract configurator instead of making tree not editable

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.

product_contract/wizards/__init__.py

@@ -0,0 +1 @@
+from . import product_contract_configurator