FIXES: distinction between switch options and mandatory args;
end/startDate specify time ranges; description doesn't correspond to an
exact match; added ongoing switch to select only the ongoing downtimes
FIXES: distinction between optional switches and mandatory args; added
some filters
FIXES:distnction between optional switches and mandatory args;
start/endTime specify ranges; added 'ongoing' switch to force 'select'
requests to select only ongoing downtimes;
FIX: date manipulation made with DIRAC Time.py
FIX: date manipulation made with DIRAC Time.py
FIX: check a control on datetime input format for switches start/endDate
Merge pull request #1909 from avedaee/av140414-v6r11

[rel-v6r11] Av140414-v6r11