GitLab

 - ASSERT added to unit-tests
 - packetFromCapture() created
 - comments changes

dhcp6 unit tests were failing to build due to an extraneous copy of the
destructor ~DhcpSrvTest.

 - comments updated
 - whitespaces cleaned up
 - minor refactoring in DHCPv6 Srv

 - removed unnecessary filename reference
 - setting Pkt6 fields is now done in a common function
 - methods return shared_ptr instead of raw pointer

Also added spaces around some operators.

 - non-const getPools() renamed to getPoolsWritable()
 - docs update

 - allocateLease6 => allocateLeases6()
 - consts added
 - consts removed
 - comments added, expanded, clarified, capitalized

 - Dhcp6Srv fix
 - unit-tests written
 - Added DOCSIS3.0 relayed traffic unit-test

Suggested by Michal in #2750, reviewed by me.