+ The event slice unpacker doesn't correctly extract element from the
slice. The indexed arguments are not ignored as they should be
(the data offset should not include the indexed arguments).
+ The `Elem()` call in the slice unpack doesn't work.
The Slice related tests fails because of that.
+ the check in the loop are suboptimal and have been extracted
out of the loop.
+ extracted common code from event and method tupleUnpack
This significantly reduces the dependency closure of ethclient, which no
longer depends on core/vm as of this change.
All uses of vm.Logs are replaced by []*types.Log. NewLog is gone too,
the constructor simply returned a literal.
