Value Summary Donut: change details display to better represent IOU/IOU markets

cross currency, same gateway: BTC bitstamp / USD bitstamp

• no change to representation (BTC/USD bitstamp)

same currency, cross gateway: USD bitstamp / USD snapswap

• USD bitstamp/snapswap
• color of gateway names = donut color

cross currency, cross gateway: USD bitstamp / CNY rippleCN

• currencies on the first line, gateways under
  USD / CNY
  bitstamp rippleCN
• or something like that, its too long to have on one line
• color of gateway names = donut color