first CRAN release

'selectDWD' uses index information to find files matching a path or station criteria.
With the returned path/file names, 'dataDWD' and 'readDWD' download and read data.
'dirDWD' and 'fileDWD' control that no file will be overwritten and path messages are useful.
'indexDWD' lists all the files on the FTP server with DWD data.
'createIndex' uses that list to create 'fileIndex', 'metaIndex' and 'geoIndex'.
'mapDWD' is an interactive leaflet map also useful to explore datasets.

Note: 'dataDWD' and 'readDWD' were started in June 2016 within my misc package
berryFunctions, from which they will be deleted after rdwd is on CRAN