Support construction lines in x-T or x-RH profile diagrams

[ghorwin]

x-y diagrams should plot additional elements that utilize the chart scale engine.

Basically, it should be possible to register vertical lines for given x-coordinates. The line series chart should plot these underneath the series using the current x-coordinate axis scale div.

PostProc should have a user interface component where users can add their own construction line coordinates.

When available, construction lines from the geometry file should be extracted to initialize the coordinate list.

[ghorwin]

Duplicate of #110