* refactor: move tr_tracker_http_announce() helper funcs into their own namespace
* refactor: move tr_globalIPv6() helper funcs into their own namespace
* refactor: move tr_address_is_valid_for_peers() helper funcs into their own namespace
* refactor: make tr_address_compare() a private method
* refactor: rename tr_address::isIPv4() to is_ipv4()
* refactor: use snake_case for tr_address methods
* refactor: make tr_address_is_valid_for_peers() a member function
* fix: save log level, encryption mod, preallocation mode as ints
* fix: ensure log level is saved in tr_sessionGetSettings()
* fix: ensure the right verbosity row is selected
