Prune provably-unspendable outputs
[raw] reject insanely high fees by default in sendrawtransaction

There have been several incidents where mainnet experimentation with
 raw transactions  resulted in insane fees.  This is hard to prevent
 in the raw transaction api because the inputs may not be known.
 Since sending doesn't work if the inputs aren't known, we can catch
 it there.

This rejects fees > than 10000 * nMinRelayTxFee or 1 BTC with the
 defaults and can be overridden with a bool at the rpc.
Use 'low S' as malleability breaker rather than 'even S'
Add michagogo to gitian download scripts
Adjust weight for michagogo in gitian download scripts

Following a discussion in #bitcoin-dev, around
19:00 UTC, 20132209
Merge pull request #2949 from gmaxwell/fewer_fee_footguns

[raw] reject insanely high fees by default in sendrawtransaction
Merge pull request #3023 from Michagogo/pgp

Add michagogo to gitian download scripts
Merge pull request #3016 from sipa/lows

Use 'low S' as malleability breaker rather than 'even S'
Merge pull request #2791 from sipa/proveprune

Prune provably-unspendable outputs