Support for hdate parameter required in weather-dl tool

[ksic8]

For single date parameter, user may provide multiple hdate values.

ECMWF URL:
https://apps.ecmwf.int/archive-catalogue/?stream=enfh&levtype=sfc&expver=1&month=jan&year=2021&date=2021-01-04&type=pf&class=od

In the sample MARS request below, user is looking for 20 years of historical data for the given date parameter.

class=od,
date=2021-01-04,
expver=1,
hdate=2001-01-04/2002-01-04/2003-01-04/2004-01-04/2005-01-04/2006-01-04/2007-01-04/2008-01-04/2009-01-04/2010-01-04/2011-01-04/2012-01-04/2013-01-04/2014-01-04/2015-01-04/2016-01-04/2017-01-04/2018-01-04/2019-01-04/2020-01-04,
levtype=sfc,
number=1/2/3/4/5/6/7/8/9/10,
param=165.128/166.128/167.128,
step=0/6/12/18/24,
stream=enfh,
time=00:00:00,
type=pf,
target="output"```