Manager for characteristic curves

[TobiasRosskopf]

A topic which came up last developer online meeting:

It would be great if BlueM.Wave could read/write/edit/plot curves which are NOT time depending (such as waterl-evel-discharge-relations, water-level-volume-relations, etc.)! For this it would make sense to implement an extra module or manager to handle this. The TeeChart-Plugin is also able to plot these.

One step further, the characteristic curves could be used in analysis functions (for example calculate discharge time series from a water level time series).