Automate Testnet chain_id

[relativityboy]

As a testnet running unique code, I want to have my own special pony chain_id so that a successful connections to with a new node means that node knows about my special unique code, and so that my developers are not having to field "background noise" level tech questions when they could be spending that time making my software or infrastructure better.

AC

• every testnet deployment gets its own unique chain id
• optional - the chain_id incorporates the git commit hash
• optional - the chain_id incorporates the hour/minute of day the chain was launched
• optional - bonus points for implementing both the the previous 2.

[inertia186]

I just wanted to note, from the perspective of someone using the testnet under different re-deploy scenarios.

If we change the chain_id and an app uses the previous one, the error message would be something along the lines of "missing posting authority" (serialization failure).

If we just restart a testnet without changing the chain_id, the error message would be something along the lines of "unknown key" (can't find the post you're attempting to vote on), if there's an error at all.

[relativityboy]

I believe chain_id switch is primarily helpful for people running nodes. To handle api errors 'nicely' steemd would need to check for it specifically after throwing a "missing posting authority" error. Hm, I wonder if the performance hit would be too high, and if we could instead encourage client libs and apps (beem / hivemind) to check for this before submitting transactions, @mvandeberg?