Duplicate "Energies" Futures Ticker Shortcut to Energy

[jaredbroad]

Expected Behavior

Energy isn't countable should not use plural in shortcut.
Futures.Energy.BRENT_CRUDE,

Actual Behavior

Futures.Energies.BRENT_CRUDE,

Duplicate the energy shortcuts to make it backward compatible.

Checklist

• I have completely filled out this template
• I have confirmed that this issue exists on the current master branch
• I have confirmed that this is not a duplicate issue by searching issues

[Martin-Molinero]

Reopening after reverting associated PR which was breaking pep8 support, see issue #8080 .
self.add_future(Futures.Energy.BRENT_CRUDE) use case should continue to work, should add unit test asserting this