The minor issues addressed are:
- Missing comments
- Lack of todo
- Log messages

Also, fix getting requested option codes from ORO.

 - config parsers updated
 - new unit-tests for vendor options written
 - libdhcp++ cleaned up
 - fixes in option_vendor.cc
 - comments added and cleaned up

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

Also, use Ciaddr instead of Yiaddr to get the released lease from the
lease database.

 - hooks documentation updated
 - dhcp4 message logs updated
 - long lines wrapped in dhcp4_srv.cc
 - unit-test names now use camel notation
 - Pkt4::bufferOut_ renamed to buffer_out_