Integrate with Cosmos for Bounties/Hacks

**Fronte End Notes**

- Add chain to bounty + hackathon creation forms (staff flag)
- Funder should be able to create bounty with Cosmos
- User should be able to start / stop / submit work with Cosmos
- Funder should be able to payout using web3
- Validate Cosmos wallet addresses
- Funder should can create and payout Cosmos bounties
- Hunter can start and submit work with Cosmos

**Back End Notes:**

- Transaction verification
- Changes to bounty creation + editing endpoints
- Testing
- sync_pending_fulfillments cron can verify casper transactions
- bounty API can support creation and editing of Casper bounties