use warehouse._get_mto_route to get the MTO route

instead of using a custom lookup with a different implementation
closes #2608

pass context as a named argument
[IMP] Change documentation + new action_consume/qty/origin corrections

Simplify the action_consume of the consumption lines after the corrections
by Kevin Wang.  Also the UoMs are revised as the action_consume uses the default UoM
of the product.

We have to avoid circular boms where a child bom should not contain the product that
represents the parent bom, but it is possible for example to use another product of the parent bom in
the child bom.

As the consume line move has no procurement rule, its origin will have no description.  So, when there is
none it will also check the description of the previous move (when passed to procurement for example) This way
the chained moves or purchase order for example will have the MO-number as origin and not nothing.

[IMP] Change assignation

[IMP] UoM changes continuation

[IMP] Make sure we can use 2 times the same product in a BoM

[IMP] Source document for consume lines to procurement
[IMP] Update module descriptions of procurement and product_extended + _bom_find and properties

Module description of procurement was deprecated (talking about mrp, ...) and in product_extended
it described things not implemented in the module.

In _bom_find, we passed a UoM which was not used in Saas-4 and it would not be logical that you
need to select a BoM that matches the UoM, so I removed it.

In the demo data, there was still a push rule which triggered a move from output to pack.  The copy=False
is correct for production_id when you would have these push rules.

For the properties: we want to allow to take a bom which has no properties, but only when there is no other
BoM matching the properties we pass.

Update module descriptions

[IMP] production_id copy + no round

[IMP] _bom_find without uom, property correction
[FIX] mrp: solve bom structures views

A previous refactoring brought a bom_line_ids field on the mrp.bom, thus
deprecating the _child_compute method. But the previous refactoring did
not go through all the views, breaking everything that relied on the
_child_compute (tree view, report). As the bom_line_ids refers to the
mrp.bom.line model (introduced by this previous refactoring, note:
_child_compute returned mrp.bom record) and that we can't make a treeview
showing different model, this patch introduce a function field _get_child_bom_lines
on the mrp.line model, allowing to go through the bom_line_ids of a mrp.bom.line
if this mrp.bom.line refers to a mrp.bom.

[IMP] Rename bom_line_ids to child_line_ids in mrp_bom_line to avoid confusion
[IMP] Better demo data + property comment