Grant that updates on files in the local ownCloud folder are automatically uploaded

[davivel]

AC:

• no matter if the files are "available offline" or not
• changes should be checked in the files contained in a folder where the users browses in, or do a pull down
• changes should be checked for all the local files in a full account sync

NOTES:

• automatic retries of failed uploads should be considered in the resolution of this issue; could be included or not
• this issue doesn't cover uploading new files in the local folder; that's in #1663