Everywhere including examples, external interop APIs, bindings generators
code and in other valuable places. A couple of `interface{}` usages are
intentionally left in the CHANGELOG.md, documentation and tests.
The usage of the Blockchain's one leads to the same ExecFeeFactor within
a single block. What we need is to update ExecFeeFactor after each
transaction invocation, thus, cached DAO should be used as it contains
all relevant changes.
