Add 'State of the Gateways' feed in News section

**Is your feature request related to a problem? Please describe.**
Several assets issued by gateways operators cannot be deposited / withdrawn using Bitshares wallet. Experience is very confusing for new users and disturbing or inconvenient also to experienced users.
Examples:
You can deposit rudex.STEEM using reference wallet, but withdraw only using rudex wallet.
You can deposit or withdraw rudex.GRC only through rudex gateway

**Describe the solution you'd like**
Feed with messages on the current state of the gateways would help to find cause of the problems instantly and without posting questions on several forums and social channels. Example feeds (**not necessary true in the current state of the network or gateways, for illustration purposes only**):
- rudex.STEEM - withdrawals possible using only rudex wallet
- rudex.GRC - deposits and withdrawals possible using only rudex wallet
- open.GRC - gateway under maintenance since 01/12/2017 - deposits and withdrawals not possible
- openledger - average ticket response time 17 weeks

Start by locating the News section and how its existing feeds or messages are assembled. Clarify where gateway status data would come from and how it should be represented before implementation. Done means the News section presents current deposit, withdrawal, maintenance, and response-time information for gateways.

Written by the indexing model from the issue text.