Support for time series diagram with trilean values

[elfring]

Trilean values can be displayed by chart software in principle. I hope also that ternary data can be configured and presented in more convenient ways for clearer diagrams of multiple time series.

• Variations exist for the representation of this data type. Can any known conversions become built-in for such input data?
• Intermediate increments should not be displayed as in comparison to regular line chart types. Specific lines or filled rectangles should be shown in lanes.