Adding some error checking to FieldTest_CSVCreator

At beginning of CSV creator for the Field Test raw files, we need to
check that the functions received a legitimate folder path (folder that
contains the raw data), outputFilename (if the file exists, warn that
we will overwrite it), and that the options given are in a string. The
numbers in the string “options” will determine what values are put into
the CSV.

Also, declared column header values. The number above them in a comment
is their “option number”. If that number is found in the arg “options”,
those values will be put into the CSV.

The script can be run with no options (will ask user for location of
raw data and where to save CSV), one option (assumed to be the folder
path to the raw data, and will ask user where to save the CSV), or 2+
options (assume that first is folder path to raw data, and second is
where to save the CSV).