Allows self signed certs

Subsequently found out that you can enable self signed certs by dragging the certificate file onto the emulator, which allows you to install it on that device. I still feel this PR is still valid for development purposes where you aren't able to do this.

* Adds an option to allow self signed certificates
* Overrides connection:canAuthenticateAgainstProtectionSpace and connection: didReceiveAuthenticationChallenge to use new option.