Add tasks to run fit/combine commands and tools within cf environment.

[jomatthi]

This PR adds tasks that run the different steps for the fitting procedure to calculate top tagging SFs and the impacts of the nuisance parameters on the fit:

• topsf.CreateWorkspace: sets up the workspace using a datacard and a physics model
• topsf.GenToys: generate toys using the workspace and set parameters
• topsf.MultiDimFit: performs a multi dimensional fit, expected, with and without frozen systematics
• topsf.PostFitShapesFromWorkspace: calculates expected pre- and postfit shapes
• topsf.Impacts: calculates expected impacts and collects them in a .json file
• topsf.PlotImpacts: plots the impacts for each POI

A sample bash command that should trigger the whole workflow:

args=(
    "--version" "${version}"
    "--poi" "SF__0o1q__UL17__pt_300_400,SF__2q__UL17__pt_300_400,SF__0o1q__UL17__pt_400_480,SF__2q__UL17__pt_400_480,SF__3q__UL17__pt_300_400,SF__3q__UL17__pt_400_480"
    "--inference-model" "uhh2"
    "--producers" "weights,features"
    "--topsf.CreateWorkspace-pt-bins" "pt_300_400,pt_400_480"
    "--topsf.CreateWorkspace-physics-model" "topsf.inference.combine_physics_model:topsf_model"
    "--topsf.CreateWorkspace-merge-scenarios" "3q:ThetaLike,2q:ThetaLike,0o1q:ThetaLike"
    "--topsf.MultiDimFit-fit-name" "_exp"
    "--topsf.GenToys-freeze-gen-parameters" "SF__0o1q__UL17__pt_300_400,SF__2q__UL17__pt_300_400,SF__0o1q__UL17__pt_400_480,SF__2q__UL17__pt_400_480,SF__3q__UL17__pt_300_400,SF__3q__UL17__pt_400_480"
    "--topsf.GenToys-set-parameters" "SF__0o1q__UL17__pt_300_400=1.,SF__2q__UL17__pt_300_400=1.,SF__0o1q__UL17__pt_400_480=1.,SF__2q__UL17__pt_400_480=1.,SF__3q__UL17__pt_300_400=1.,SF__3q__UL17__pt_400_480=1."
    "--topsf.GenToys-gen-name" "_toys"
    "--topsf.Impacts-asimov-data" "True"
    "--topsf.Impacts-do-initial-fit" "True"
)

command_to_run="law run topsf.PlotImpacts ${args[@]}"
confirm_and_run "$command_to_run"

In addition to the task files, a simple bash script confirm_and_run.sh is included in this PR that asks the user whether to skip a command or to run it, even with additional parameters.