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.
This allows to reuse it across different packages.
testchain can't be used because of circular dependencies.
Init() is not changed except for filepath.Join() use instead of direct string
appends which is a better approach anyway. rootpath is required because
current directory will change from package to package.
