Get rid of automatic registration, rename things

IPCSSLContext is now SSLContext.
SSLContext is in an anonymous namespace.
It is create by ipc::initialize_ssl_context() that is called
explicitly by ipc::init(). That avoids any any
global constructor issues and allows to catch exceptions.

The creation of the custom sslContext can be prevented
by setting TDAQ_IPC_SSL=0. The default is to install it.