We used to launch a thread for API server inside the wallet crate, now we do it inside api crate, so the cmd tool launches API and exit. This fix makes sure that command will wait for API thread.
* Middleware and handler (mw implements the same trait) could be attached to multiple nodes inside the router
* Middleware could be attached to the router (syntactic sugar, it is attached to the root node) as well as to any node
* Handler's call method receives an iterator of handlers and responsible for calling the next handler if needed
* Support TLS in ApiServer
This is ground work to support TLS in Grin APIs (like wallet ot node). Particular API implemention needs to decide if TLS is used or not and pass certificate data etc.
* P12 format support
* New method to start TLS server
* Transparent TLS support in API client (depends on URL scheme http/https)
* Refactoring
* Initial support for graceful shutdown (commentred out int this PR, unstable for now)
* API server tests (TLS server test is disabled by default, hyper client rejects self-signed certificates, so extra step is needed to install local CA (I used mkcert)
* Add a cert file to make test complile
