This image will be for developing locally on your own laptop.

By default, login will use Shibboleth.  But there is a new
settings variable (USE_SHIBBOLETH_LOGIN) which, if False,
will instead activate password-based login, which is best
for development on a laptop or such.

This will be useful since we plan to build multiple images for
various purposes. So, we create a new directory, docker/,
which will have a subdirectory for the configuration for each image.

Not sure why these were generated. The models were not modified,
but maybe it was just because we are now using Python 3, and string
handling has changed compared to Python 2.  I think all of the fields
that were touched have strings in them either as a default option
or as a set of choices.

Use voeventparse instead of VOEventLib

This is necessary since we use --system-site-packages to create
the virtualenv, and the system version of numpy is too old.

* Switch from VOEventLib to voevent-parse due to significant
  string-bytes issues in VOEventLib
* Remove bad exception handling in events API for creating a
  VOEvent
* Add parameter checking to events API for creating a VOEvent
* Combine VOEvent building code for events and superevents into
  a single instance which handles both cases

Also, use Python 3.5 instead of Python 3.7 - I think we're going
to be using 3.5 for a bit since that's default for Debian 9.

For Python 2, we install VOEventLib from a git fork since upstream
is not Python 2-compatible.  But we don't need to do that for Python 3!