change sp2gp into sp2gpl to interpolate surface and pressure level variables onto the same grid

Solves issue #10 @jgarcia @fdoblasreyes @lpcaron 

See merge request !4

Develop bugs

Hi,
  
   I have just fixed a minor bug which created a wrong file naming in some cases : fc was missing from the file name so that the number of the previously processed member was not correct.

Best regards
Virginie

See merge request !3

Develop bugs

Hi,

   I have just corrected two small bugs in nccf_atm_monthly. There was a $ missing in front of a MONF. And there was a renaming of the leadtime dimension to time whether it had already been done on my file so I added a check to skip this step is the renaming is already done.

Best regards
Virginie

Commented a concatenation of the old file with the new file while they had the same name; only if they span different forecast times the files should be concatenated

Bug-fix: the variable leadtime is already in the file, the dimension leadtime is not hence -v should be -d

Bug mix members

Merge branch 'bug-mix-members' of https://gitlab.cfu.local/cfu/atmosphere_diagnostics into bug-mix-members