Feature/new returns fixes

[eleanorshakeshaft]

What does this do?

Fixes:

• Instead of using "Actual Price" to calculate the refund it's now using "Gross"
• Change confusing "payeeIsClient" to "payeeIsRetailer"
• Dates not appearing correctly
• Minor rewording

  How should this be manually tested?

• Put through a Non-EU order (ie no VAT) and process a full refund for it.
• Put through an order with a discount and process a full refund for it.

  Related PRs / Issues / Resources?

n/a

Anything else to add? (Screenshots, background context, etc)

This does not fix VAT issues with exchanges, see https://github.com/messagedigital/cog-mothership-returns/issues/163

[irisSchaffer]

Sorry I am interrupting this, but I just found out that Uniform Wares have a view override where they use payeeIsClient(): uniform_wares/view/Message:Mothership:OrderReturn/return/balance/balance.html.twig

So we have to change this in UW before this can be merged in.