..Line2DPlot: adding formula support to enable use of arrayOf

Signed-off-by: Kunal Shroff <shroffk@bnl.gov>
..Line2DPlot: selection support, simply use the y pv.

Change-Id: I6ebd0b8030a2126e08f76cf13238f6b2233b2202
Signed-off-by: Kunal Shroff <shroffk@bnl.gov>
..Line2DPlot: fixing NPE

Change-Id: I874d9a4c89ae6d8a9df89083755ee13b49238275
Signed-off-by: Kunal Shroff <shroffk@bnl.gov>