dropbox: increase chunk size to improve upload speeds - fixes #103
dropbox: increase chunk size to improve upload speeds - fixes #103

Chunks aren't buffered in memory, so chose 128M as the default size as
producing the maximum throughput.  This takes the throughput from 78
kBytes/s to 4MBytes/s a 50x improvement!

alexcouper/rclone,ncw/rclone,olihey/rclone,simlelievre/rclone,seuffert/rclone,kynikos/rclone,greendayo7/rclone,olihey/rclone,X1011/rclone,jackschmidt/rclone,jackschmidt/rclone,B4dM4n/rclone,ncw/rclone,simlelievre/rclone,B4dM4n/rclone,kynikos/rclone,simlelievre/rclone,X1011/rclone,B4dM4n/rclone,yonjah/rclone,greendayo7/rclone,ncw/rclone,arcimboldo/rclone,greendayo7/rclone,seuffert/rclone,jackschmidt/rclone,klauspost/rclone,Blackfin/rclone,alexcouper/rclone,greendayo7/rclone,Blackfin/rclone,seuffert/rclone,kynikos/rclone,arcimboldo/rclone,olihey/rclone,Blackfin/rclone,arcimboldo/rclone,alexcouper/rclone,kynikos/rclone,klauspost/rclone,ncw/rclone,yonjah/rclone,B4dM4n/rclone,arcimboldo/rclone,seuffert/rclone,klauspost/rclone,olihey/rclone,yonjah/rclone,jackschmidt/rclone,X1011/rclone,yonjah/rclone