Pyjabber

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* Changed default database path. Now, it will create a *Pyjabber.db* file in the working dir where the server is launched
* Fixed, refactored and sped up the STARTTLS process. Now there's an independent worker (async task), who awaits from a queue for TLS upgrades petitions from StreamHandler objects.

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* Update the README + HISTORY

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* Added Uvloop for unix-like os (improved loop event, compared to default asyncio loop)
* Fixed Windows bug with Ctrl+C and not being able to stop the server.
* Changed the async treatment of the server. Now the function start() returns a coroutine, and must be launched from ``asyncio.run()`` or similar

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* Fix previous release

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* Added Pubsub XEP (Service discovery, create node, delete node, publish, subscribe and retrieve subs)
* Added Service Discovery XEP
* Added Dataforms XEP
* Added --database_purge flag to reset database (erase any register)
* Refact singleton scheme
* Refact XEP scheme (migration to singleton)
* Create shared variables via contextvars
* Different refacts to the code

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* Updated depenencies version