[NGRM] Well log viewer - plot legend abbreviation

[mirisb]

The following enhancements is requested from our clients:

• When log name is very long, clients would like the log track legend to display a short version of the name, or sometimes not show any legend (mostly for the case of stacked tracks that can only display a single log).

Suggestion:

• Enhance TemplatePlot interface to contain also legendText (or similar name) to be used for the legend.

[mirisb]

relates to #2472