This alignes the OnOff cluster with the LevelControl cluster in terms of signal behavior: Previously, the OnOff cluster would fire a generic commandSent() signal for some commands and specific signals for others. Effectively forcing the user to connect multiple signals even if only the command would be of interest. The LevelControl cluster instead always fired a generic commandSent() signal and *additionally* more specific signals for parsed parameters. This changes the OnOff cluster to be in line with the LevelCluster as and making the API a bit simpler to use when parameters are not of interest. Also it completes the specific parsing for all 3 clusters.