Refactor: change all `private <variable>` to `#<variable>`

[mylinhdao]

As described in #315 , we should apply this change in every typescript file:

• use #statementsSuperSet instead of private statementsSuperSet, since the last one does not transpile the variable to private correctly. We may change that in every metric.

[mylinhdao]

After discussing in team, I think we will not implement this. Because the private modifier works in TypeScript code and it should be secured enough. We never touch the transpiled JS code at all so we don't need to take care if the access modifier are correctly in there.