Git doesn't save empty dirs, so put a placeholder there that is
ignored when the test data is copied to its final location during
testing.

This was never updated when timestamps were changed from floats to
ints.

This doesn't affect anything in nilmdb, but is needed by nilmrun.

Some pylint errors are worth fixing; many are not.

We now have full coverage of the main code.

This used to have problems with older CherryPy versions, but the
current one seems to handle it just fine.

With this solution, we can catch it cleanly in the standalone
nilmdb-server, and test the error paths in our normal test suite.

It works again now.

This is hard and finicky to test, so there's unfortunately not a clear
way to get 100% test coverage in cherrypy_start.  However, that
function is only used in the test suite and the standalone
nilmdb-server script, not in production (which goes through wsgi and
skips all this cherrypy server stuff entirely).

Non-embedded mode is not used in the test suite or wsgi server;
it was an option in the standalong nilmdb-server script, but it's
really not necessary, and removing it gets rid of some untested
code.

Note that argcomplete is also now required.

This is optional and helps with development.  If we ever need/want to
support systems without Cython, this can be wrapped in a
try/except:pass block (and the .c files can be included in the
MANIFEST.in so that source distributions include them).

This is a pretty big simplification: the user should first use pip to
install everything in `requirements.txt`, and we no longer try to
cater to cases where Cython is missing, etc.

This was in setup.py to reduce litter in the root directory, but it's
simpler to keep it how it's supposed to be.

simplejson was there for python <= 2.6 compatibility.
It's not needed now, and installing it with pip can lead to segfaults
because pip is dumb.
(see e.g. https://github.com/simplejson/simplejson/issues/114)

We don't actually use nilmdb.utils.threadsafety.verify_proxy in the
main NilmDB code, but it's useful for finding errors.

It found an issue with __getattr__ in SerializerProxy which
(1) can't be avoided?
(2) is now commented in the code
(3) shouldn't matter in real use