Ethereum: Utility function to parse ERC20 Tokens

[jornfranke]

ERC20 tokens are standardized currencies on the Ethereum block chain (cf. https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20.md). Although one could directly parse them without any issues in any Big Data applications, it could make sense to make them as part of the library since they have many applications.

Examples, unit and intregration tests need to be provided.

[jornfranke]

Since compiled Ethereum contracts cannot be decompiled back to Solidity or other source code containing the variable name, we can identify an EC20 contract by the hash values of the method signatures and an EC20 transaction by the use of the hash value of the "transfer" method signature