[IMP] website_sale: fast checkout if no distinct shipping address.

Change flow for checkout.

Allow to specify during the billing address if you want to use the same address
for the shipping. If it is the case, we bypass the address selector step.

Use last shipping address by default

Re-add right column for lg-screen

Fix checkbox terms, which was at the wrong place and checked by default

Payment: allow to add back button, and choose position of icon

Courtesy of:
   fgi for specs, re-specs, re-re-specs and testing
   sri for help to design new progress-bar

Task-39062