zapit must check for existing zapit sessions before starting if user asked for python mode

[raacampbell]

Have a python setting. If user sets to true, the start_zapit function must do:

try
    matlab.engine.shareEngine('zapit')
catch
    disp('CAN NOT START.... BLAH BLAH')
    return
end

This will ensure Python can always find Zapit.

[raacampbell]

Done 3ed04d72958a8da1c45d211650c7782bf11aecc0