upload: Add a option to the upload command

This patch adds a TTL option to the upload command. This TTL is reported
on the server side. A cron script on the server will delete the file
once it exceeded its TTL.
upload: Change the uploaded file name

The uploaded file name which contains the age limit for each uploaded
file is now renamed to uploaded-limit.
upload: Add the server side script

With the clean function, the upload script now comes in two parts. First
the client side and second the server side which resides on the server
and clean the uploaded files when needed.
umons-schedule: Add the script umons schedule

This script is used to clean the ICS file provided with the new calendar
application we use at UMONS.