dhcp4: dhcp progress notifications

Output some basic log messages depicting dhcp4 operations.
dhcp6: dhcp progress notifications

Output some basic log messages depicting dhcp6 operations.
man: wicked7 updates

Remove mention of wicked.7 as we currently will not be shipping
a wicked-devel package. (bnc#877322)
man: wicked8 xml updates

XML configs are not yet officially supported, so ifcfg is still the
standard.
doc: README updates
Merge pull request #271 from kmroz/bnc874609
Merge pull request #280 from kmroz/wicked7