Simple Assets v1.4.0

• re-delegate assets. (lender of assets can allow them to be re-lent)
• New parameter bool redelegate added in delegate action, which allows asset re-delegation.
• New field bool redelegate added in table delegates => require migration in case of self- deployed contract !!!
• In undelegate action parameter from was removed. (identity of borrower is available in the delegates table)
• Fixed transfer of empty assets array
• Error messages improved for clarity
• Code refactoring