This field used to be assigned by the filter system and returned through
the RPC API. Now that we have a Go client that uses the underlying type,
the field needs to move. It is now assigned to true when the RemovedLogs
event is generated so the filter system doesn't need to care about the
field at all.
While here, remove the log list from ChainSideEvent. There are no users
of this field right now and any potential users could subscribe to
RemovedLogsEvent instead.
In this commit, core/types's types learn how to encode and decode
themselves as JSON. The encoding is very similar to what the RPC API
uses. The RPC API is missing some output fields (e.g. transaction
signature values) which will be added to the API in a later commit. Some
fields that the API generates are ignored by the decoder methods here.
