0.0.5 host metronome

Created by: bmarv

this pr introduces a metronome, that can be configurated by the host and results in an auditive and visual feedback regarding the configured beats-per-minute(=bpm), tact-nominator and -denominator. The metronome audio can be muted and the metronome can be stopped. When a metronome has been configured and started, the host can invoke a broadcast-start to start a metronome instance with the respective constraints for every connected client. Additionally the recording of the client starts as well. Both stops, when the host sends a broadcast-stop message to all clients. Then the resulting video-file will be saved and can be identified by the client-id and time-stamp in the filename.