Create new CustomDecimalField for handling float inputs better
than they are handled in rest_framework.fields.DecimalField.

CommaSeparatedOrListField is now called DelimitedOrListField.
Default delimiter is ',', but the user can specify anything.
Some improvements to not show [] in web forms by default and
properly handle empty inputs.

Moving a few base class throttles and fields from the events app up
one level so that they can be used elsewhere.

Moved events.api and superevents.api into the new api app.
We want to have a versioned API, so these are now in
api.v1.events and api.v1.superevents, respectively. Part of this
change is that we require a custom reverse function (api_reverse)
for handling versioning. Much of the required code changes for this
migration include converting reverses to use this function and
changing relative imports appropriately.

GetParentObject and SupereventParentMixin are now full viewsets
rather than just mixins.  They also get the parent object during
the initial phase of request processing, cache it, and are able to
check object permissions on the parent.

Created ChoiceDisplayField - same as ChoiceField, except its
to_representation() used the display value instead of the key.

New CommaSeparatedOrListField type which accepts a comma-separated
string (and splits it into a list) or a list input.  Useful for
handling input from the web interface as well as from the Python
client in either form.