Allow option for self-signed certificates

[marohrdanz]

When sending ngchms to a shaidy server (via HTTP requests), the code does not allow for a self-signed certificate on the shaidy server. In general, this is the desired configuration. However during development, a shaidy server with a self-signed certificate is common.

As a convenience to other developers, make these requests configurable such that:

• default is to require a valid certificate on the shaidy server
• a flag can be set to allow for a self signed certificate

Example: the GET requests in chmCreateServer().

[marohrdanz]

Perhaps we don't need this. In my own development, when needed, I set:

httr::set_config(httr::config(ssl_verifypeer = 0L))

This allows me to make requests to services with self-signed certificates.