Expand get_top_markets API to return more data fields

[abitmore]

Expand get_top_markets API to return more data fields, specifically, the fields returned by get_ticker API. Or create a new API to return vector<market_ticker>.

Other than that, we still need to think how to improve the APIs to avoid being spammed / manipulated, as discussed here: #560 (comment).

Please discuss.

[abitmore]

There were some (maybe useful) comments in #924.

#924 (comment) by @jhtitor:

I have 2 cents from bitshares-qt standpoint.

First of all, the get_top_markets API itself is a great idea, and I'm really glad we finally have such a feature. Going to use it extensively.

Secondly, I think it would be great, if the API could be expanded to allow setting base asset. Say, a user is interested in trading OPEN.BTC -- I want to show top OPEN.BTC markets. The current behavior (listing everything) is also extremely useful, so I'm not proposing to replace it.

Sorry if this is the wrong ticket, which only deals with the return format.

#924 (comment) by me:

I too want to leave something here for reference, but don't want to write a feature request yet:

• https://api.crypto-bridge.org/api/v1/ticker
• https://cryptofresh.com/api/asset/markets?asset=BTS

[oxarbitrage]

closed by #1549