Add src revision control software

(cherry picked from commit 5c7c63af66d5b772d97d5ffda09df9cf2ef96f8b)
all-packages: add gitMinimal, use it for nix-exec and fetchgit

since git is used to bootstrap a lot, this can save lots of waiting
time.

(cherry picked from commit 3630b985553d1ebf3fe0d5c3ba0b62927e16f257)
vimrsi and vimsensible