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

Makes the life of packagers and everybody who wants to build this
easier.

Closes #25.

That's what the README suggests and - more importantly - the cmake
config file works with.
Also use angle brackets instead of quotation marks in two cases.

- Add initial version of crypto bot
- Add spdlog as dependency

On Windows std::optional requires C++17