add various new magit config

- Use "remote/branch" format
- Show refined diff in status buffer
- Don't show details of untracked directories
- Restore window configuration on quitting a magit buffer
- Tell evil magit-commit-mode is for editting
use proportional font for editing commit message
update key bindings for git committing

- magit-commit-mode is now for viewing commit, not editing, so remove
  its custom key bindings
- make git-commit-mode treat "saving" as "committing"
tweak appearance of  some git stuff

- Less into-your-face git blame's headers
- Better color/size for editing git commit