Minor update to fix some bugs - potentially breaking change

• Resubmit to CRAN
• Corrected variable names to not be similar to a corresponding command (FFdownload -> FFdata, tempdir -> tempd). This is potentially a breaking change, so I additionally included a warning message when the package is loaded.
• Also corrected date in converter for annual data to Dec of each year.
• Additionally fixed the download/download_only problem which now should be working