Add context menus

[jovannic]

This is really great.

I wanted to use the animated visualizations in a small presentation on git usage for non-command-line users. Not sure if you'll want this, but I added context menus for the basics on commit nodes and branches (commit (if head), reset, checkout, merge, rebase) and on origin (fetch, push, pull).

The node/tag menu uses historyview functions directly because historyview doesn't reference commandbox, and so you can do things on origin too. The origin menus use commandbox.command, mostly because they fail more frequently and I wasn't sure what to do with those errors. Didn't want to refactor or change the dependency graph on my own. Thoughts?

Used https://github.com/patorjk/d3-context-menu

[onlywei]

This is interesting. I will try to find time to code review this, but I don't find that I have a lot of time these days to do so. Please do not be offended if this takes a long time.