Allow users with sufficient points to informally create new tasks

[shuesken]

In order to increase serendipity in the community, let appropriate users add minor one-time-tasks for the next auction. Appropriate could mean any user who has been participating for long enough or who has received above-average points the week before. Minor tasks could mean fixed one-time-tasks set at a low enough price, or new tasks up for auction. These tasks could both be ones that the user deems necessary for the overall community, but that would be too infrequent to show up on the auction (e.g. "cleaning up dead leaves") or just general niceties (e.g. "organising supplies for Christmas decoration" or "update the website" or "spray this wall").