Vault contract updates

[markspanbroek]

Updates to the API of the Vault contract as worked on in logos-storage/logos-storage-contracts-eth#220

Most important changes:

• token transfers are much more restricted in the vault, improving its safety
• when a storage request fails, only the providers at fault are punished, the rest are not
• when a storage request fails, the client is only reimbursed for the remaining time in the contract
• no longer possible for the marketplace to request one final storage proof before allowing withdrawal
• repair reward is temporarily stored with the client's funds while slot is free, and not yet filled; this could lead to a client withdrawing repair rewards when slots are free when the request ends