Default task sorting - Trending

Friends, while it may look as the order in task table is borken, it is not :)

Please kindly note it's just a new default mode of sorting have been introduced. You still can switch to sorting by id or amount of solvers using the select above the table.

The new mode tries to improve the situation when newly introduced tasks dangle in the bottom of the list simply because there are no many solvers yet. It is especially lamentable about many cool problems proposed by colleagues.

The Trending order is based on both how long the task is being with us and how many solvers it has:

ordering_score = (total_tasks - this_task_id) / (this_task_solvers + 1)

In case anyone may want to propose the formula to be improved somehow (perhaps by making some part of it non-linear) here is the list of tasks in tab-separated form, for experiments.

Instead of using id the real task age was considered (task creation date is not stored for now, but we can use the date of first successful solution) - however there was prolonged period when tasks were added only rarely and I decided against using dates.