Light state visualization for partially set light states

[thomassedlmayer]

See this comment in #119.

If a OSI message contains partially set light states, both indicator and brake lights are visualized (as being off) even though they are set to the type UNKNOWN (which means they were not set). In such cases the visualization does not correctly represent the data.

[jdsika]

I think this is a rather easy fix which can be done next?