Remove seeding of UiTask and UiTaskSet.

Extracted from PR #264

Even though PR #264 is attempting to completely remove UiTask and UiTaskSet, I thought it might be worth it to approach it in baby steps. :baby_symbol: This PR just focuses on removing seeding of UiTask and UiTaskSet as a first step.

All of the specs pass, and I ran the server, clicking all over both with the admin user and a limited user.  I created reports and widgets.  Not sure what else to check.

@dclarizio Please review and merge if you're happy with it.

cc @jrafanie (check the deletes)