Permission handling added

- Updated section 4. Security and privacy considerations
- Added interface TCPPermission (UDPPermission and TCPserverPermission remains but wants to get feedback before going further)
- Editorial corrections
https://github.com/sysapps/tcp-udp-sockets/issues/81
Do you have any ideas on how to communicate the effect of granting access to various endpoints? What sorts of things should UAs consider including in their dialogs?