a LOAD_STATUS 'REQUEST' value is available, but for some reason wasn't
being used.  This is the appropriate place to set it, right when the
request is received.  Hopefully this makes it easier to track load
status.

When running tests on headless systems that don't have a proper terminal,
older versions of python-git in the archive tests will fail with:

...
  File "/usr/lib/python2.7/dist-packages/git/util.py", line 120, in get_user_id
    username = os.getlogin()
OSError: [Errno 25] Inappropriate ioctl for device

This is because getlogin requires a terminal for various reasons.  This
issue was fixed in later versions of python-git.

Loop to caget daemon channel, will succeed only when channel is
retrieved.  Not necessarily faster, but should be more reliable on
slower test hosts.

This moves all node daemon supervision to the systemd supervision
system.  nodes are instances of a guardian@.service template, all
under the guardian.slice.

Logging will be handled by journald.  An svlogd interface is kept to
interface with the old logs.

The guardctrl interface is rewritten appropriately, and the web server
control interface is dropped in favor of ssh-based remote access.

This allows guardian to me imported without needing ezca installed.

The drawback of this is that we no longer export the ezca version through
the CAS.  I don't see this as a particularly big loss.  If really needed
we could push it from the worker up to the daemon via the shmem interface,
and from there push it into the CAS.

store an 'archive' flag in the guarddb, so the full list of archive channels
is:

  [chan for chan, data in db.guarddb if data.get('archive')]

This involves moving the _N and _S channels back into the db
definition, which I think is not tragic.

Apparently the change in 2456a737 did have a
negative impact after all.  python3 requires all relative imports to
be explicit, which is presumably why they drop the level=-1 option.
But the option is still needed for python2.

Rather than try to recreate the defaults just capture them with
**kwargs and pass them on appropriately.  Fixes #3.

This removes the provided scripts in favor of using setuptools entry_points.
This requires modifying the tests to not depend on the previously provided
scripts.

somehow python2/3 difference

fixes error in python3

newer networkx versions don't have the same problem.

don't require loading daemon (since it imports ezca for not particularly
good reason), but requires enumerating options explicitly
here.

would be better if daemon didn't import ezca

python3 has builtins, instead of __builtin__ in python2.  This is mostly a
straight compatibility.  "reload" is not a built-in in python3, so we have
to also pull that from importlib.

This is NOT an overhaul of the whole import custom import handling, it just
allows for guardian to be imported by python3.

This includes one change that could affect python2: setting default level=0.
python3 builtins.__import__ does not support level=-1, which tells import
to automatically handle both absolute and relative imports.  Since we're only
doing absolute imports it should be safe to set this to 0.  Hopefully this
won't cause any problems.

This latest pcaspy release fixes redundant updates after initialization

This cleans up how REQUEST and REQUEST_ENUM records are updated, to
eliminate possible redundant updates.