Add automatic relation of SO line and logisitc route based on sourced_by field.

Wee look for the PO related to current SO line by the sourced_by fields.

If the PO has a destination location with usage "customer" we apply the dropshipping route to SO line.

If the PO has a destination location with usage "internal" we apply the make to order route to SO line.
to help me understand a failing test, rephrase it

To figure out what is the assertion, I used some harmless gherkin-like
wording.
adapt the test to test the new onchange

We are now green again, and the test looks more readable to me.

On the other hand, we lost the test for the warning in case of
inconsistent PO destination as SOL route.

I am not convinced this check is still necessary. It does no harm still:
we seem to always follow the happy path.
document why the dropshipping dep was added again
Merge pull request #56 from nbessi/routes_in_so_line

Add automatic relation of SO line and logisitc route based on sourced_by...
Port sale_quotation_number to v8
fix api decorator on _popup_exceptions

This method returns an action dictionary, and with api.one a list was
returned. For that reason no window was displayed. Fixes #59
fix: create() returns a model instance in v8
refactor _popup_exceptions a bit
fix pylint warnings

rename local variable and arguments shadowing other identifiers
Merge pull request #61 from gurneyalex/8.0-fix-pylint

fix pylint warnings
refactor Class -> class_model
Merge pull request #60 from lepistone/fix-display-exception

Fix display exception
fix future exception for dropshipping

In a previous commit by yours truly, I disabled the stock-based checks
in dropshipping situations, as was suggested in #47.

The idea was correct, but the method future_orders_are_affected needs to
return False to skip the check (it means that future orders are _not_
affected, and we are cool).
bump version to 1.1
add test: for dropshipping, assume we can deliver
test dropshipping sale doesn't affect future sales
refactor common setup
add docstring to test setup, and move to the top
Merge remote-tracking branch 'upstream/8.0' into 8.0