True C++ support in exchange

[egelja]

So this isn't that hard actually. We just need to tell our users to upload a statically linked so library. Then we don't even have to worry about libc or libstdc++ differences. We just dlopen and call the functions we want.

I will take this issue. Goal is to get it done by the "dress rehearsal" run of NUTC. We sorta have support with #97 and #98 (but its very jank, either going cpp -> py -> cpp or requiring an execv call, respectively).

What needs to be done to get this working is:

• Add algo type info to firebase (@stevenewald you'll need to help me with that one)
• Make the wrapper aware of different algo types
• Add code to wrapper to dlopen a shared object and run its methods
• Add code to linter to check for expected functions in the shared object and test if they work
• Provide sample C++ project

The API with consist of four functions:

• set_order_callback
• on_trade_update
• on_orderbook_update
• on_account_update

The first one just allows us to tell the users' code what function they need to call too place an order. We will provide this for them.

[stevenewald]

Shelved for now unless @egelja wants to implement this e2e - can't spare bandwidth on the rest of the team

[egelja]

I'll do it - no ETA though.

[stevenewald]

deadline june 25

[echavemann]

lol