Multiple Gravity instances on one chain

[jkilpatr]

The Gravity design is fully compatible with essentially all EVM chains, this opens up the tempting possibility of having a bridge to many EVM based chains running at the same time.

This comes with some caveats

Protocol issues

• Collateralization becomes hard to determine. Gravity bridge depends on the value of the staking token for the Cosmos chain being higher than the total value of assets in the bridge. By adding many bridges to the same chain we are reducing the amount that can safely be in any one bridge and amplifying the existing issue of dealing with a bridge where it is more valuable for the validators to collude to steal all the funds in the bridge than it is to continue validating.

Code issues

• Find a way to easily have several instacnes of the same module running, each with unique store prefixes and token prefixes on the chain. Refer to Modify prefix to account for the potential of having multiple gravity instances on one chain #246
• Multi relaying and multi orchestrator, dynamicly submitting signatures for many chains at once