merge the remainder of project-management branch
separate developer opt-in and tips visibility testing concerns

* re-instate features/developer-opt-in.feature

it was realized that the original features/developer-opt-in-for-tips.feature
    did indeed test an aspect that ./features/view-tips.feature did not
    namely whether a tip actually exists for an unknown user
    the view-tips feature only tests whether any such tip is visible or not
    the original developer-opt-in scenarios were recreated and elaborated on
    including what happens after a previously unknown user signs-up