Feature/multi freq plot

This is a major refactoring of the survey line edit pane to allow any number of frequency plots to be viewed at the same time and to optionally see the intensity profile on the right side.  
need to add core plotting, depth_line creation, and depth line hdf5 writing (probably add a group to the survey_line group.)

one problem was that in order to use the separate=True dictionary from sdi reader i had to read it again with that set.  ideally there is an option that provided the frequencies separated with their trace nums and everything else unseparated.