Update TinyMCE to version 4.8.3

Enhancement #2737 Track order status changes

Update several development dependencies

Added setting for calculating offer discounts over the price including tax.

Update ipython to 7.0.1

Update django-extensions to 2.1.3

Update pillow to 5.3.0

Update whitenoise to 4.1

Update django-debug-toolbar to 1.10.1

Update django-debug-toolbar to 1.10

Update Psycopg2 dependency.

Optimize Range checks, and fix missing excluded_products in range.all_products()

This change fixes the inconsistency with range.all_products() which
didn't check for exclusions when includes_all_products is set

Every other bit of oscar expected range.includes_all_products means
that all products are included, no questions asked. The dashboard
interface even hides the option to edit/remove individual products.

The short circuiting in ConditionalOffer.products() is removed so
the range.all_products() logic is applied consistently.

When packages like oscar-wagtail redefine the Category model,
it can include a lot of extra CMS field data. These affect the
performance of the range lookups, while only a few fields are needed.

Cache the categories, so a range can be tested against a set of products
without refetching the categories all the time.

Also avoid querying product.get_product_class() as the Range.classes is
typically empty (it's not exposed in the Oscar dashboard interface).
It could even avoid another query if there was an API like
product.get_product_class_id() but this could cause compatibility problems for
projects that override product.get_product_class()

The range.all_products() uses range._category_ids() which performed 2 queries
where it only needs one, and can now reuse cached data.

Calling range.is_reorderable also fetched unneeded children, but this was
hidden in the RangeProductListView due to the reuse of cached data.

Update django-extensions to 2.1.2