Ensure workorder sequence is applied on new workorders

Test sequence is applied for multiple operations
Rewrite _reset_work_order_sequence in a more pythonic way
Change _order of mrp.workorder to use sequence
Set sequence on existing workorders after module install

mrp_workorder_sequence/__init__.py

@@ -1,3 +1,4 @@
 # License LGPL-3.0 or later (https://www.gnu.org/licenses/lgpl.html).
 
 from . import models
+from .hooks import post_init_hook