Reference events multiple hops forward or backward in time

[myedibleenso]

It would be useful if lingbot could retrieve events further forward in time (ex. next next), rather than just the closest upcoming event. Querying past events might also be useful.

This gist shows one way to add such support along with a unified event framework: https://gist.github.com/myedibleenso/dd92a747d6dfd45ff77e3073a27af97d

It has only been tested on the following queries:

• next
  • the nearest upcoming event measured from the current time
• next nlprg
  • the nearest upcoming NLP Reading Group measured from the current time
• next next
  • the event following the nearest upcoming event
• nlprg next
  • the same as next nlprg
• nlprg next next
  • the nlprg following the nearest upcoming nlprg
• next next next
  • the event following the event following the nearest upcoming event
• previous
  • the event most recently past (last would probably be better than previous)
• previous nlprg
  • the NLP Reading Group most recently past

In the command repetition in this implementation is unrestricted.

Anyway, I'm happy to go the PR route with this feature if there is interest.

[Trevortds]

Made a new feature branch. Will discuss with @jdukatz soon.