One dimensional objects should be supported both as Mesh+PC plot and Curve plots

[markcmiller86]

Is your feature request related to a problem?

A topologically one dimensional object is a path of some sort (one parametric dimension) in any number of geometric dimensions. A march along the real number line (1D geometry), a circle in the plane (2D geometry) and a helix in space (3D) are examples of such a path.

We should allow for users to visualize these kinds of objects both in geometric space and parametric space (e.g. as an xy curve). For the example of a march along the real number line, the parametric and geometric cases are one in the same and there is no need to populate (pollute) the mesh and pc variable menus with them.

But for cases of 2 or more geometric dimensions, we should allow users to plot those objects both as Mesh+PC plots and in parametric space as ordinary, xy curves. The default parametric varable could be distance along the path. Alternatively, the data producer may have written a variable on the 1D path object that represents the parametric variable and the xy curve plot should be able to use that (as the x coordinate).

Here is a 2D example in original (left...which is a 2D PC plot) and parametric (right...a simple xy curve plot using distance as the parametric variable) spaces

One way to implement this is to enhance avtTransformManager (which is the first layer to "see" data from database plugins), to add Curve surrogates for every topologically 1D object. In addition, the Curve plot could be enhanced to allow the user to specify the X coordinate variable to use (from among all the variables specified for the 1D object).