Plot jdx files

Plots a (selection of) jdx file(s) in a new or specified figure.

h=plotjdx(variable,h) Plots a (selection of) jdx file(s) in a new or specified figure. If no file is specified then the function ask for user to select files...
input 'variable' can be:
- a 'filename' of a jdx file,
- a cell with filenames to several jdx files or
- JCAMPStruct to be plotted in
input figure handle 'h' is optional