Rebasing

[Cretezy]

It would be great if lazyjj would support rebasing.

How I envision this working:

1. On the "Logs" tab, the user can select the change which will be rebased
2. After doing a keymapping, a menu asking if they want to rebase the entire branch or just that change would be shown. This would map to -b or -s of the rebase command, respectively.
3. Once a change and method was selected, the user would scroll to select the destination, then press enter to rebase

While the rebase is happening, the source would stay highlighted, and most other actions would be disabled. Escape would cancel.