This change comes along with the new tests for DHCPRELEASE in the
separate file, and having a separate test fixture.

Before creating NCRs the code used to check if there is a match
between a new and old lease and refused to send NCRs if there was
no match. This was wrong behavior because the allocation engine
could be reusing other client's lease in which case there could
be no match whatsoever and the NCRs should still be generated.

Do not remove duplicates if other MessageInitializers held them.
Also, do not remove message from the dictionary if removing the
duplicate.

- Renamed getMilliseconds to getLastMilliseconds
- Renamed getMicroseconds to getLastMicroseconds
- Added time units to hooks messages descriptions
- Fixed some typos

    Adds bad-packet logger to DHCPv4 server

Objects passed by reference and todo instead of TODO.

The limit had been introduced when the message pointers were held
in the array (having a fixed size). With recent changes the array
has been replaced with the list. Since, the list is dynamically
allocated there is no need for fixed size.

Fixed, copyrights, typos, minor clean up items