Add log of operations for interactions with every stored contract

[Robbepop]

With the current Canvas UI it is very hard to keep track of how you have operated on all your stored smart contract instances in the past. For this is would be very nice to have a log of commands (e.g. sent messages with their parameters and their returned values or if they failed and why.)

There should be a log per smart contract but also it should be possible to merge logs of different selected smart contracts. The logs should be displayed in chronological order.

Maybe some interface similar to a console but with proper encoding and decoding support would be what users would probably be most familiar? @erler what is your stance on this from a design perspective?