[3512] Bare bones implementation of the iface selecting class.
[3512] Implemented IfaceCfg::openSockets function.

Also, added better documentation for the IfaceCfg class.
[3512] Added unit tests for invalid interface names being selected.
[3512] Implemented support for unicast sockets selection in IfaceCfg class.
[3512] DHCP servers now use the IfaceCfg class for selecting interfaces.
[3512] Minor tweaks in the logging of warnings when socket fails to open.
[3512] Loopback interface should not be selected for DHCP traffic reception.

Also, fixed selection of the unicast addresses for receiving DHCP packets.
[3512] Set SO_REUSEPORT option when opening multicast socket.

This is required on NetNSD and OpenBSD so as multiple sockets can be bound
to in6addr_any and dhcp server port.
run tools/reorder_message_file.py on the mes files

(This is a test of new git server :)
link to mailing lists webpage

(another test of git server migration :)
Merge branch 'master' of ssh://git.kea.isc.org/git/kea
[master] Merge branch 'trac3477'
[master] Added ChangeLog entry for #3477.
[3501] Corrected error messages reported when configuration error occurs.

Also, removed multiple references to DHCP4_CONFIG_LOAD_FAIL from the
DHCPv4 server and DHCP6_CONFIG_LOAD_FAIL from the DHCPv6 server.
[master] Compilation fix for comparison of std::stream pos value.

This is trivial fix so as I am committing it on my own discretion. Also,
this fix had already been reviewed and applied on master branch but
apparently disappeared after the recent git migration.
[3512] Renamed IfaceCfg to CfgIface as suggested in the review.
[3512] Addressed review comments.
[master] Fix for master being out of sync

Conflicts:
	ChangeLog
[master] Fixing master after git server migration.

Conflicts:
	ChangeLog
Merge branch 'master_fixed'