Flint: Rework plot select
Closes #2093 (closed)
This MR provides a small rework of the handling of plot select in order to make it safer.
- This fixes the
plotselect
behaviour for the default curve plot. Including after the start up of Flint. - This provides some how a persistence of extra items added manually on the plot
- Plus other few things
Edited by Valentin Valls