Upgradable contracts

[kostysh]

It will be good to have upgradable smart contracts structure. It means that if some sub-contracts was changed and has been deployed their new versions it will not cause changing addresses of main contracts (Pandora, PandoraMarket)

[Koroqe]

New version of set of contracts should be redeployed with reputation migration. Workers, kernels, datasets should be moved to new Pandora contract manually