indent on description
use a tab before the keyword type.
use two tabs before the committer username.
line too long

the latter is relatively new and doesn't work for all of our supported
python versions.  will fix a buildbot report.  committing at my discretion.

the original version didn't have a problem because the constructor
should never be used in python wrappers, but I do this to silence cppcheck.
the change is small anyway.

as this seemed to be a controversial move.

- small updates to doc and comments
- changed __try_login to _try_login
- replaced direct calls to print() with self._print(), to override in tests
  (and more easily check output)
- added some more test cases
- made cmdctl tests fail is environment vars aren't set

Conflicts:
	src/bin/dhcp4/dhcp4_srv.cc
	src/bin/dhcp4/tests/dhcp4_srv_unittest.cc

Conflicts:
	doc/guide/bind10-guide.xml

Conflicts:
	src/bin/dhcp4/config_parser.cc
	src/bin/dhcp6/config_parser.cc
	src/lib/dhcpsrv/dhcpsrv_messages.mes
	src/lib/dhcpsrv/memfile_lease_mgr.cc

some test cases needed to be adjusted accordingly.

so that we can share it with test cases for findAtOrigin.
no behavior change so far.