Add encoding and decoding of constructors and option to include deployment data

[rmeissner]

It would be really useful to be able to create deployment transactions. For this the deployment code (init code) is required and it should be possible to encode the constructor data.

Another useful feature would be to decode constructor data, so that deployment transactions can be analysed.

As this are potentially large strings that are copied into code it should be possible to deactivate this as a compiler flag (or even better specify the contracts that should include their deployment data)