Sync but check for last modifide date

[ncw (Nick Craig-Wood)]

@ncw

Here are the new flags for rclone check

Flags:
      --combined string   Make a combined report of changes to this file
      --differ string     Report all non-matching files to this file
      --dst-only string   Report all files missing from the source to this file
      --match string      Report all matching files to this file
      --src-only string   Report all files missing from the destination to this file

The combined report puts a symbol in front of each file, +/-/ etc (haven't written the docs for this ye

For sync/copy/move --differ would mean files that existed on both sides but needed to be transferred. --match would be files that existed on both sides but didn't need to be transferred.