API Coverage

[sheldonth]

There are plenty of methods in the C++ library not covered by this library yet. Let's use this issue for discussing which are most desired.

[qrpike]

• It seems the C++ docs specify that ATCreateQuoteStreamRequest accepts an array of symbols. May be more performance than a separate subscription for each symbol.
• ATCreateTickHistoryDbRequest Would be nice since the HTTP service caps data sizes.