Add Staking to Bao on xDAI

Now that the staking contract has been tested as Bamboo on BSC we can confidently shift a similar set up to xDAI should the community approve.

On xDAI we would launch two staking contracts, one ready to go and another still needing development:

1. xBAO: xBAO will operate like xSUSHI or BAMBOO and perform distributions on the fees collected from the Baoswap contract on xDAI. Users will user Bao.cx for staking on this.

2. sBAO: sBAO still needs further designing but the goal is for sBAO to be a permanent staking solution. Where users will burn their Bao for a stake in the pool and over time get token distributions from the other franchise ecosystems. Similar to the model used by Yearns yveCRV vault. This staking will be done in Bao.cx.

At some point in the future if experiments with $RHINO perform well the community can also consider migrating $RHINO as a third staking option.

Unlike $RHINO, sBAO is very dependent on the existence of franchises returning governance value to the main Bao ecosystem (Bao and Bao.cx) given this it is not a suitable candidate for testing on BSC and will need to be developed straight into the xDAI ecosystem.

This proposal recommends that we use Bao.cx for the staking rather than "Bao on xDAI" this is because the "Bao on xDAI" is automatically created by the validators of the Omnibridge as an ERC677 token when migrating. This means that it cannot be owned or managed by a Bao multisig/DAO. While this is a decentralized validator process, the best way to make the risk minimum is to use the Bao.cx ERC20 token that Bao produced for the xDAI farms and maintain the 1:1 swap which has mostly finished its testing.

This proposal will also further help to balance the demands for Bao.cx with mainnet Bao.