Adding root histogram example to analyze pane
@uplegger -- Again from @masizemo who we will soon start having making these MRs directly.
- Added histogram plotting directly into analyze pane. Still need to decide what plot is most useful and when/how this pane should be updated.
- Some cleanup
See https://gitlab.cern.ch/UTKCMS/ModuleScorecard/-/merge_requests/8 for more details.