ndscope-test can now show "scatter" plots.

Plot one channel against others.  Each plot can have one channel giving the X value, and any number of channels giving Y values.  The plot will show one trace per Y value channel using the color of that channel.

Create a scatter plot from the command line by running "ndscope-test --scatter <x-channel> <y-channel-1> <y-channel-2> ..."

Create a scatter plot from a time domain plot.
1. Right click to get the pop up menu.
2. Select configure channels.
3. Select at least two of the channel names in the window with Control + click or Shift + click. The first selected channel is always the X channel
4. Press the Add Scatter Plot button at the bottom of the screen.
5. Press the OK button.

The timespan of the traces matches the time span of the traditional time-domain plots. Pan and zoom a time domain plot to 
change how much is shown on the scatter plot.

WARNING: This is a development release.  

There may be bugs.

Some bits are not working for scatter plots.  For example, the configure channels window does not appear for these plots.

Some needed interface is not yet included.  There's no way to change the X channel for a scatter plot yet, other than to 
open a new window and add the new X channel to the command line.  Scatter plots cannot be saved to or configured in yaml files.  Many more bits aren't done.