[pig] Editor broken if Hive app not installed due to autocomplete

The Pig Editor breaks if beeswax app is not installed.

In: apps/pig/src/pig/views.py

In def(app), the app.mako render sets the autocomplete_base_url as:

'autocomplete_base_url': reverse('beeswax:api_autocomplete_databases', kwargs={}),

When beeswax is not installed this will break the Pig Editor. It should check for the existence of beeswax and set the autocomplete_base_url as empty if beeswax is not installed.