Notebooks - set up paths to use environment variables better

[jyoung3131]

Right now we explicitly set the path to the tools in the notebook. It would be great if we could read this from a file or pull it from the environment variables. Unfortunately Slurm-launched jobs often won't have the correct "LUCATA_BASE" set as an environment variable.

import os

#Set the path to the latest toolset 
LUCATA_BASE="/tools/emu/pathfinder-sw/22.09-beta" 

#Get the path to where all code samples are
os.environ["USER_NOTEBOOK_CODE"]=os.path.dirname(os.getcwd())
os.environ["PATH"]=os.pathsep.join([os.path.join(LUCATA_BASE,"bin"),os.environ["PATH"]])
os.environ["FLAGS"]="-I"+LUCATA_BASE+"/include/"+" -L"+LUCATA_BASE+"/lib -lmemoryweb"

Ideally we'd like to read LUCATA_BASE from a file in the repo so we can more easily update for future toolsets.