cbrestore: Provide a format description for fields '--to-date' and '--from-date' and also an example

Provide a format description for '-to-date' and '-from-date' in help output of cbrestore.
The current ./cbrestore --help output just lists:
--from-date=FROM_DATE
restore data from the date specified. By default
all data from the very beginning will be restored
--to-date=TO_DATE restore data till the date specified. By default
all data that are collected will be restored

Also, please provide an example usage.