Provided sample designs (e.g. `easy-mode.js`) should include `hidden_fields`

[jkuester]

When writing reports in the CHT, some fields can be automatically hidden from the user when looking at the report on the Reports tab.

For our sample scripts, we should also include the hidden_fields property when writing reports so the reports are displayed in the same way on the Reports tab as reports written normally. This will help avoid confusion.