Fix Issue #658 - BTS Trade Button (#662)
Fix Issue #658 - BTS Trade Button (#662)

* View Trading Icon for BTS
- Only when Preferred Unit is not BTS
- Otherwise, display an empty cell

* Small cleaning

bitshares/bitshares-2-ui,bitshares/bitshares-ui,bitshares/bitshares-ui,BitSharesEurope/testnet.bitshares.eu,bitshares/bitshares-2-ui,BitSharesEurope/graphene-ui-testnet,BitSharesEurope/graphene-ui-testnet,BitSharesEurope/wallet.bitshares.eu,BitSharesEurope/graphene-ui-testnet,BitSharesEurope/testnet.bitshares.eu,BitSharesEurope/testnet.bitshares.eu,BitSharesEurope/graphene-ui-testnet,bitshares/bitshares-ui,BitSharesEurope/testnet.bitshares.eu,bitshares/bitshares-2-ui,bitshares/bitshares-ui,BitSharesEurope/wallet.bitshares.eu,BitSharesEurope/wallet.bitshares.eu,BitSharesEurope/wallet.bitshares.eu