Fixes to XML basket
Fixes include:
- Support for multiple discounts and better support for no discounts.
- Filtering of the basket item names (for valid characters and overall length).
There is a unicode dark shadow hanging over the validation, I feel, but I think unicode is something to tackle across the board in OmniPay anyway. For the record, Sage Pay will now accept UTF-8, and will make a good attempt at converting it to its internal ISO-8859-1 characterset. This is a new thing for Sage Pay (quietly introduced 2015) so it takes some of the characterset encoding issues out of our hands.
Source: PR #53