Also fixed whitespaces in some recent entries.

This patch has been proposed by Alexis Fidalgo. It was earlier reported
that Kea always appends a dot at the end of the hostname which may cause
some clients to fail on processing this option.

Simplified the method which loads leases from the CSV file.

- copyright year updated
- comment clarified
- added @todo in Pkt::setHWAddrMember()
- getMACfromDocsis*() don't use intermediate members, will accept
  options with length 1

Also, prevented opening the optional lease files if they don't exist.

Also added an utility class to bulk load leases from the file.