Adding option NAMING to the USER spatialInterpolations algorithm

Adding option NAMING to the USER spatialInterpolations algorithm, which allows to specify the file naming convention using YYYY for year, MM for month, DD for day, hh for hour, mm for minute, ss for seconds (optional) and PARAM for meteo parameter.

So for example:

TA::algorithms = USER
TA::user::naming = YYYY-MM-DDThh.mm_PARAM

would search for files 2018-12-31T23.00_TA.ext

The default is set to YYYYMMDDhhmmss_PARAM in order to not break existing setups (this was the previous required naming scheme for the USER algorithm).