Support FA accounts in IB Broker

[tibkiss]

Interactive Brokers provides 'Financial Advisor' (FA) accounts, which groups multiple accounts together. These accounts currently are not supported by zipline-live.

The support could be easily achieved by:

1. extending broker-uri with an optional account code. e.g.: --broker-uri localhost:7492:111:DU32145
2. store the specified account code in IBBroker's constructor (if specified)
3. set the m_account when placing an order:

   zipline/zipline/gens/brokers/ib_broker.py

   Line 664 in 7c68fb4

   order = Order()

[githubbla]

So this is implemented already?

[florentchandelier]

refer to #104