Conflicts:
	ChangeLog

 - Guide updated
 - Iface::addUnicast() now refeses duplicates
 - addUnicast and clearUnicasts are now commented
 - new unit-tests
 - argument for addActiveIface is const reference again
 -

Also, clear the output buffer in the Pkt4 and Pkt6 every time when pack()
is called.

Conflicts:
	src/bin/dhcp4/dhcp4_srv.cc
	src/lib/dhcp/libdhcp++.cc

 - exceptions are now more verbose

Conflicts:
	ChangeLog
	src/bin/dhcp4/tests/dhcp4_srv_unittest.cc

 - 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.

Conflicts:
	src/bin/dhcp6/tests/dhcp6_test_utils.h

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