[BT] Removed unused Q_OBJECT decls.
[BT] Removed useless PLUGINS_BITTORRENT_WIN32_LEAN_AND_MEAN
[BT] Removed Plugins subnamespace.
[BT] Use init lists.
[BT] Moved session settings management to SessionSettingsManager.
[BT] Removed unused serialization ops.
[BT] Enum class for settings presets.
[BT] Code style.
[BT] Removed unused property binding.
[BT] Unified scrape settings.