python suport in zingg

[sonalgoyal]

We need few ways in which python run should work

a. some phases are python only. like assessModel. we want a way to run them through Zingg. script should not have any knowledge of which phase is python or not. the client program should handle the logic of appropriate invocation

b. some phases are user scripts and example programs

this needs to run in all environments - zingg package, dev and release. also docker