A few changes for python3

This merge updates some of the python code to increase the python3 compatibility. There are two commits:

• [964a3882] update print statement usage to print() function calls
• [eeb14648] update some imports/renamed variables

Could someone more familiar with python and megaplot have a look at this?

assigned to @meg.millhouse

added 31 commits

• eeb14648...425e2807 - 30 commits from branch lscsoft:master
• 998f0483 - Merge branch 'master' into 'python3'

Compare with previous version

merged

mentioned in commit 545e77d0