[IMP] delivery: basic pluggable support for shipping integration

Add a `delivery_type` selection field on delivery.carrier.
The default is `grid` i.e. a static pricing grid with rules
to compute the delivery costs.

Future module will however be able to extend the `delivery_type`
selection to add new keys, such as `fedex` or `ups` and provide
custom implementations for the various API methods, as described
below.

In order to add your own external provider, follow these steps:

 1. Create your model MyProvider that _inherits `delivery.carrier`
 2. Extend the selection field `delivery_type` with a pair
    ('<my_provider' , 'My Provider')
 3. Implement API methods as required:
    <my_provider>_get_shipping_price_from_so
    <my_provider>_send_shipping
    <my_provider>_open_tracking_page
    <my_provider>_cancel_shipment

1 files changed, 1 insertions, 0 deletions

diff --git a/addons/delivery/__init__.py b/addons/delivery/__init__.py
index d9f5b50644d..c33ce66418b 100644
--- a/addons/delivery/__init__.py
+++ b/addons/delivery/__init__.py
@@ -23,3 +23,4 @@ import delivery
 import partner
 import sale
 import stock
+import models