Fix met workflow

- cleanup of download code
- fix dbfile.input.insert to work correctly

@mdietze @jam2767 @bcow 
met2cf.XYZ should take start_year and end_year, since there might be more years in the database than the user is interested in, or should take list of inputs_id's to get the files from the database.

met2model.XYZ should take start_year and end_year, since there might be more years in the database than the user is interested in, or should take list of inputs_id's to get the files from the database.
Shouldn't this have a check to installed.packages as well so we don't download rhdf5 every time we run install.dependencies.R?