Add removed field to Log JSON

[iostat]

Fixes #336

This is a fairly trivial change, especially considering Ganache will never reorg and thus the removed property is moot (which reasonably explains its omission in the first place).

However, for those of us who care whether or not a log was reorged as part of their application logic, and aren't using JavaScript (i.e., care about well-formed JSON-RPC responses and can't use the truthiness of log.removed === undefined), this lack of removed renders Ganache unusable as a Web3 provider.

[davidmurdoch]

Looks good. I'd like to see a simple test to check the value of the field before merging though. Is this something you can do?

Aside: this field has also been added in a separate branch where we are rewriting ganache-core: https://github.com/trufflesuite/ganache-core/blob/4a081acfad686e2f94c49f6087df6bb9722d2d1d/src/chains/ethereum/src/things/blocklogs.ts#L137. We do plan on stimulating reorgs in the future.

[iostat]

Hope that was a reasonable place to put the test. I didn't want to add an entire transaction flow just to test the presence of a field, and the headline of test suggested it's appropriate anyway.