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.
Which greatly simplifies reuse of these packages (and they're expected to be
reused since real tokens implement standards and also add something of their
own) and allows to avoid effects like
doc_test.go:68:28: ambiguous selector neoContract.BalanceOf
when neo.Contract is used. Avoids duplication in NEP-11 implementation as
well.
