Added support for deleting files (the previous version only supported removal of folders).

For the script to delete files instead of folders, the "f"-flag should be used when executing the script, e.g.:

./cleanup.sh -d /mnt/online-storage-01/dbbackups/prepared -t 10380 -f -v
(Will delete files older than 10380 minutes located in the "prepared"-folder.)

NOTE! When running the script using the "f"-flag only single files will be deleted. Folders will stay untouched.