Blame: More improvements needed!

[goran-w]

• Add tooltips for the Back/Fwd arrows.
• Add a drop-down from the navigation history bar, to list the commits and quick-select one!
• Show block-row hover-highlight, as in all other selectable lists!
• Show commit-info tooltip for full block-row, not just for hash!
• (On hash, let tooltip instead/also explain what happens if we click it?!)
• (Possibly show commit-info within Blame-window layout, and/or improve the commit tooltip.)
• Add "age-coloring" of (commit) line-blocks, as in Plastic SCM "Annotate". (And indicate line-block borders always?)
• Show previous commit (1st parent / HEAD)
• Show 2nd parent (added/deleted/renamed)
• Ignore whitespace
• -M -C
• (Compare features in web-blame?)

Some improvements were implemented in Hackathon-issue 1 via PR sourcegit-scm#1408.

May need some further work, here are some helpful docs / tips:

• https://www.atlassian.com/git/tutorials/inspecting-a-repository/git-blame
• https://medium.com/@drdmason/git-blame-all-the-way-back-62957f8407
• https://medium.com/@drdmason/git-what-really-changed-1b0e89c32de5