Port of the old periodic tests view

Still using legacy database, as we didn't decide how to move to the new instance yet.

To do:

• switch to DataTables for the advanced features (as for the old page)
• add periodic tests management features (start, creation)

Note that to use this view we have to add a Mango index:

{
  "_id": "_design/index-by-start",
  "language": "query",
  "views": {
    "time_start-json-index": {
      "map": {
        "fields": {
          "time_start": "desc"
        },
        "partial_filter_selector": {}
      },
      "reduce": "_count",
      "options": {
        "def": {
          "fields": [
            {
              "time_start": "desc"
            }
          ]
        }
      }
    }
  }
}