Enable title & description. Add argparse options.

 * Title and description hardcodings were not used. Added them.
 * Add argparse and some new options:
    --title TITLE               Title for all images
    --tags TAGS                 Space-separated tags for all images
    --description DESCRIPTION   Description for all images
    --drip-feed                 Wait a bit between uploading individual images
 * Store internal files in input directory rather than execution directory so it can be run from anywhere.
 * Some minor cosmetic things