Multi-relaychain support with their own parachains

[0x8f701]

This can be a good feature to implement when we would like to test both Kusama and Polkadot, so it looks like:

kusama:

• statemine
• parachain1
• parachain2
• ..

polkadot:

• statemint
• parachain1
• parachain2
• ..

This can be useful to implement if someone finds time to do it