core: need a way to disable dex server accounts without deleting

[buck54321]

Currently "disable account" for a server bascially deletes the account. But it won't let you do that with active bonds. We need a way to disable the account without actually deleting it and while still monitoring bonds to refund, in a similar fashion to how we can disable individual wallets.

[ukane-philemon]

I'd like to look into this.

[dajohi]

func (*core).DisableExchange(disable bool) error {} and type Exchange struct gets a Disabled bool

then core doesn't auto connect to any exchange with Disabled = true

[sysfu]

Funny because I'm trying to figure out how to permanently unregister, remove, or delete the bison.exchange dex, and I can only seem to disable it using Bison 1.0.4.