Adds function to set presence explicitly, query presence explicitly and
to set presence explicitly on sync as well as receive presence updates.

Merge device_verification from Chethan2k1/mtxclient

* Fix build Issue in the crypto_bot.cpp

* Add Linting

* Change the location of DeviceEventVistor

* Fix to_device test

* Remove iostream header

* Fix Remaining Tests

* Remove Sender and Type in KeyRequest

* Add endpoint to construct to_device messages

* Add new endpoint new_send_to_device

* Made Changes in new to_device_send

* Wait for carl's access_token

Partial update of models.  Tests are still broken and there are some other issues that need to be resolved.  Getting this uploaded so that @Chethan can take a look at what's changed and modify their proposal

On Windows std::optional requires C++17

fixes #13

fixes #14

fixes #7

fixes #9
fixes #10

fixes #3 
fixes #11