include mixing and tickerbuyer info in walletinfo

[chappjc]

For DEX we would like to know:

1. what accounts are configured as the mixedaccount and changeaccount
2. if mixing is actually enabled (csppserver && mixchange, not with the ticker buyer)
3. If the tickerbuyer is running (enableticketbuyer) because we don't want it running
4. If tickerbuyer is running, the purchaseaccount (in the off chance it's not the mixed account that DEX uses)

I think it would be ideal to have the above information available either via walletinfo or another RPC. Ideally, not one of the RPCs that has to compute balance (e.g. listaccounts or getbalance) because for large wallets these are relatively slow... definitely not getstakeinfo.

The ideal configuration for DEX is mixing configured with just mixchange, not ticker buyer (we cannot feasibly fund orders from a mixed account that is automatically spending coins for tickets). So we want to discover this as well as confirm which accounts are actually mixing/change/normal.

CC @itswisdomagain

A JSON-RPC request to stop the ticker buyer would also be of use.

[jrick]

Is this intended for use with a user-controlled cli wallet? I would imagine with decrediton, that since all of these details are managed by decrediton, they could also be provided to the dex library.

[chappjc]

No Decrediton involvement. It's not required to run DEX.