add is_sku in product model,fork dashboard.catalogue
fix the bug for attr_sku_%s in dashboard catalogue view and form
initial/save
child product set values from its parent product
show up the attr_sku options in front web
add style sheet for attribute choose
fix the bug
Merge remote-tracking branch 'origin/oscar-sku' into oscar-sku

Conflicts:
	oscar_site/oscar_site/templates/catalogue/partials/attribute_sku_options.html
fix the attribute css
commit on js
drop the front color and size choose
front sku support
fix the bug:prevent disable all inputs
drop sku front support as diffrent behiours in variours browsers