* Add blockContact and unblockContact subcommands
* Send blocked status in contacts sync
* Use only one method for blocking and unblocking
* Add blocking/unblocking for groups
* Prevent blocked messages from being printed
* Print blocked property in listContacts and listGroups commands
* Handle BlockedListMessages
* Store blocked state from incoming contact and group sync messages
* Minor changes and corrections
* Add block and unblock commands to man file (and also fix some headings of commands)