Changes:

 * A already existent file will not be redownloaded
 * If a download failes, and a link war generated, it will be retried.
 * Thread sleeps for 500ms after a download to ensure, that the file-lock has vanished
 + Estimated file-size is displayed. Estimate uses 16 bit 44.1 KHz PCM. FLAC size WILL be lower!
 * Using a dynamic Date instead of a hardcoded date-string to accomodate for different locales.