Add end date as well to sorting SQL.

Given these dates (this is what the user sees in UI):

    Entry #1
    start: DD.MM.YYYY - 20:00
    end: DD.MM.YYYY - 21:00
    
    Entry #2
    start: DD.MM.YYYY - 20:00

In database they're stored like this (end date is automatically set to start date, very good thing):

    start: DD.MM.YYYY - 20:00
    end: DD.MM.YYYY - 21:00
    
    start: DD.MM.YYYY - 20:00
    end: DD.MM.YYYY - 20:00

In this case, a DS with sorting for this field will return entries in this order:

    Entry #1
    Entry #2

This is not true, because `Entry #2` is earlier than `Entry #1` (NB: same start, but `Entry #2.end` < `Entry #1.end`). With this patch the sorting order takes into account the end date as well thus returning correct order:

    Entry #2
    Entry #1

Thanks!