Native contracts deployment creates `Transfer` notifications and adds
them into interop context. However, these notifications were not stored
for two reasons:
1. typo in `Transfer` (so these notifications were not recognised during
processing of the invocation tx in (*Blockchain).storeBlock(...) method)
2. these notifications have `from` adress setted to null, so conversion
to []byte fails. Same thing could happen with `to`.
Related C# issue: https://github.com/neo-project/neo/issues/1646
For now, made both `transfer` and `Transfer` valid.
4ebac5a069