Add created at filter to articles

Title: Add created at filter to articles

  1. Make the timekeeping available to see how many timeunits were used at a day
  2. Timekeeping is essential for hr to keep track of time used
  3. The updated_at and/or created_at is not searchable therefor no overview can be created where it lists the timeunits for the day

(I created a fork and have a fix already)