Update concurrency listener and scatterplot support for Jupyter notebook support

[khuck]

APEX needs to implement the "reset" event for the concurrency listener to:

• clear out all samples
• re-open the sample output file

Also need to add support for "grabbing" the python script to generate the task scatterplot output image. Right now it is in a script on disk, which is inaccessible to the notebook. It needs to be a constant string somewhere in the C++ code, so we can write it to a file in the virtual filesystem and then execute that file.