memory leaks in the implementation.

https://matrix.org/docs/spec/client_server/unstable.html#key-export-format

Currently, importing does not work.  Do not use this commit
if you intend to keep import/export working.  I also have not yet
cleaned up the code, so there might be some nasties that have
not been discovered.

- Remove the one time key that is used to create an inbound OlmSession.

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

Pass copies of input buffer to methods that delete them

fixes #23

fixes #21