Distributor API to add major version migration

[peersky]

Add new interface & abstract implementation to Distributor contract to configure #16 . It:

• Takes arguments:
  • distributionId
  • old version requirements
  • new version requirements
  • migrationContract address
  • Migration strategy when upgrade requested, Enum:
    • CALL:
    • will call migration contract using #15, implementation if migration contract is zero
    • DELEGATECALL:
    • let migration contract handle and execute migration on behalf of distributor.
    • Check ERC165 compatibility with interface defined in #15
    • If migrationContract is zero call implementation instead
    • use signature from #11 specified calldata appended with user arguments.
    • REPOSITORY_MANGED:
      • use delegatecall using calldata specified in #11.
      • callmigrationContract, if address is zero call implementation instead
      • if version increment is more than one, iterate trough
      • Revert if if version is downgraded
• Stores migration info: (migrationContract, both requirements) as hashmap where key is hash(distributionId,strategy,migrationContract)
• Emits events:
  • MigrationContractAddedFromVersions(uint256 indexed oldRequirementBase, uint8 indexed oldRequirement, address migrationContract, uint8 strategy)
  • MigrationContractAddedToVersions(uint256 indexed newVersionsBase, uint8 indexed newRequirement, address migrationContract, uint8 strategy)

Add interface implementation to ownable distributor contract. It:

• Can add migration contract only by owner