Documentation updates for FAPI CIBA

It will be good to update documentation based on recently added capabilities to CIBA (FAPI CIBA, Ping mode support etc). Especially sections like:

• CIBA related doc sections
• FAPI related doc sections (Adding note that we support also FAPI CIBA etc)
• Client policies (There is note that we have two global profiles, but now we have 3 profiles. Some more notes might be needed how to configure FAPI CIBA etc).

Thing to not forget to document:

• Client Notification Endpoint URL requirement (SSLRequired)
• Additional parameters of Backchannel Authentication request and the fact they are sent to HttpChannel by default