Modify the ts client to allow for an `openbook_twap` program

[metaproph3t]

I'm currently working on an openbook_twap program that sits on top of openbook_v2 and, for specific markets, feeds prices into a TWAP aggregator. These changes made the TS client more convenient to work with, and I think would be generally beneficial. They include:

• return the market's pubkey from createMarket, so that you can use the market in future instructions
• allow the client to pass the market Keypair, so that I can first generate a keypair, then generate a PDA that will be the Market's open_orders_authority, then create the market

[binyebarwe]

is this still in Draft mode?

[metaproph3t]

yeah, this is probably all I'll need, so will take out of draft mode and then open another PR if anything else