Restore previous volume when BYTM reloads the tab

[Sv443]

For example when using the "clear queue" button, the volume will be reset to the value of the initialTabVolumeLevel feature. Would be cool if the pre-reload value is kept.
In order to do this properly, there should be a function (exposed on the plugin interface too) that is used for all reload operations, and also handles the restoration of the previous video/song time.