mm: add volume minimums and sanity checks for oracle rates (decred#2937)

* add volume minimums and sanity checks for oracle rates

* tame bond asset warning

release candidate for Bison Wallet and DCRDEX version 1.0.0

eliminate bonus tiers (decred#2502)

dcrdex v0.6.2

dcrdex v0.6.1

dcrdex v0.6.0

dcrdex v0.6.0-rc2

dcrdex v0.6.0-rc1

dcrdex v0.6.0-beta

dcrdex v0.5.9