Allow developers to use their own SSLConntext ...

... if default configuration does not suffice

In my current project we have some pretty strickt requirements concerning SSL configuration, so that we cannot use the default KeyManager and default KeyStore i.e. we have to create and initialize our own SSLContext.

The change is not very elegant but minimalistic (i.e. with this I'm able to configure an HTTPs server as we need it without breaking the existing API)