Make consistent variable names in all dbs

[kellymccain28]

The first few pathogens (I believe up to SARS) used a database with a couple of mistakes in variable name spellings or definitions. First, the parameter_uncertainty_singe_type variable was misspelled in the parameter form, and second, the first and last names of authors were flipped, so the first name was stored in FirstAauthor_Surname and the surname was stored in FirstAuthor_FirstName.

In more recent versions of the database (from Zika, I'm not sure about SARS and Lassa), parameter_uncertainty_singe_type was updated to be spelled correctly: parameter_uncertainty_single_type. The author variable names were switched so the first name was stored in the first name variable and vice versa for surname. The spelling error in FirstAauthor_Surname was not fixed.

The cleaning code (cleaning.R in db_compilation) at the moment changes the correctly spelled variable to be incorrectly spelled to allow any code from previous pathogens to work. However, it would be good to update this for all pathogens so it is the other way around -- the incorrectly spelled variable is changed to the correctly spelled one.