Introduce Swiper State for the purpose of matching users

[teremterem]

• Maintain swiper state as the top level key so we can use it as partition (and/or sort) key in DynamoDB (at least while it is DynamoDB and not something else).
• Introduce SwiperUpdateContext to make swiper state accessible in handlers.
• Put Answerer instance into SwiperUpdateContext (as well as Elasticsearch client instance).
• Move swiper.py outside of common - put it along with telegram_webhook.py and include both these files into lambda package.

Additionally (if not too hard or even possible at all):

• Get rid of StateAwareHandlers class (provided that you see a straightforward way for handlers to be aware of their conversation state through newly introduced SwiperUpdateContext).

[teremterem]

Do not bother getting rid of StateAwareHandlers class - PTB conversation states have multiple levels (per chat, per user, per message) and trying to "convey" current state to handlers any other way than the way you already do (through StateAwareHandlers class) is not worth the effort!