We now check whether the object ID is an event or not, rather
than whether it is a superevent or not.  This is because the
superevent prefixes will likely be changing in the near future,
but the event prefixes are pretty well fixed.

Added functions for getting permission lists and details, as well as
exposing/hiding superevents and events to the public.

GraceDB servers will soon have a versioned API, so this commit
allows the user to optionally select which API version they want
to talk to.  There is also a safeguard which checks whether the
specified API version is legitimate and available on the server
they are using.

Require that some parameter is set to be upgraded for
updateSuperevent(), otherwise fail.

Adding superevent categories (production, test, mdc) to
createSuperevent() with default: production.  Also updated
utils to recognize superevent prefixes for test and mdc events.

Adding same hack as in voevents() to return the VOEvent file text.
This is temporary and will be removed in a future release.

Ensuring that VOEvent file text (in fake response kludge) is unicode.

Adapting createVOEvent to work with superevents. Note that this
required some server-side changes to the part of the events API
which handles VOEvent creation.  Also changed the arguments
(instead of sticking everything in kwargs) and updated the docstring.

Making writeEMObservation work for superevents; required some
changes to the events part of the server API as well.

updating function docstrings with correct signatures since they are obscured by the decorator, even with functools.wraps