Moving workspace

[dabercro]

@yiiyama How about we do something like this? I moved the workspace.py to common, and put the parameters in a separate module.

I couldn't get the diffs to work out nicely, but if you look at the two commits separately, it's much more useful.

[yiiyama]

Looks good to me! I kept it in monophoton because I wasn't completely sure if the tool is useable by other analyses.

[dabercro]

If not, I'll try hard not to break it and make another pull request.