[IMP] - Make recurrence mechanism on contract line

Make recurrence mechanism on contract line and some other refactoring

[FIX] - Keep contract_cron on account_analytic_account model

contract_cron defined with no_update option.
Changing it, will cause issue to past version installation.

[IMP] - Fix recurring_next_date default value

recurring_next_date should have start_date as default value in prepaid policy
and start_date + invoicing_interval if postpaid

[FIX] - Fix test check no journal

[IMP] - Return created invoices on recurring_create_invoice

[IMP] - Specific process to compute recurring_next_date for  monthly-last-day

fixes: #198

[ADD] - Add Post-migration script to bring recurrence info from contract to contract lines

[ADD] - Add search filter based on date_end and recurring_next_date

 - not_finished filter in contract search view
 - finished filter in contract search view
 - Next Invoice group by in contract search view

[ADD] - Add unit tests

- cases to compute first recurring next date
- contract recurring_next_date
- contract date_end

[IMP] - Improve Unit tests

contract/models/contract_template_line.py

@@ -0,0 +1,38 @@
+# Copyright 2004-2010 OpenERP SA
+# Copyright 2014 Angel Moya <angel.moya@domatix.com>
+# Copyright 2015 Pedro M. Baeza <pedro.baeza@tecnativa.com>
+# Copyright 2016-2018 Carlos Dauden <carlos.dauden@tecnativa.com>
+# Copyright 2016-2017 LasLabs Inc.
+# Copyright 2018 ACSONE SA/NV
+# License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl).
+
+from odoo import fields, models
+
+
+class AccountAnalyticContractLine(models.Model):
+    _name = 'account.analytic.contract.line'
+    _inherit = 'account.abstract.analytic.contract.line'
+    _description = 'Contract Lines'
+    _order = "sequence,id"
+
+    contract_template_id = fields.Many2one(
+        string='Contract',
+        comodel_name='account.analytic.contract',
+        required=True,
+        ondelete='cascade',
+        oldname='analytic_account_id',
+    )
+    partner_id = fields.Many2one(
+        comodel_name="res.partner",
+        string="Partner (always False)",
+        related='contract_template_id.partner_id',
+        store=True,
+        readonly=True,
+    )
+    pricelist_id = fields.Many2one(
+        comodel_name='product.pricelist',
+        string='Pricelist',
+        related='contract_template_id.pricelist_id',
+        store=True,
+        readonly=True,
+    )