git-repo: Move submodule to overlay 'public'

Move opt/git-repo to overlays/public/home/opt/git-repo.
taro: Move submodule to overlay 'public'

Move opt/taro to overlays/public/home/opt/taro.
vim: Move .vim dir and all submodules to overlay 'public'

Move .vim to overlays/public/home/.vim .
.config: Move .config to overlay 'public'

Move .config to overlays/public/home/.config .
.local: Move .local to overlay 'public'

Move .local to overlays/public/home/.local .
bin: Move to overlay 'public'

Move 'bin' to 'overlays/public/home/bin'.
dotfiles: Move toplevel dotfiles to overlay 'public'

Move $git_top/.* to 'overlays/public/home'.
build: Move dir _build -> build

Now that all stuff to install is located in "$GIT_TOP/overlays/*/home",
we can rename the silly "_build" to "build".
Merge branch 'public-overlay' into public

All conflicts are submodule directories.

Conflicts:
	overlays/public/home/.vim/bundle/align
	overlays/public/home/.vim/bundle/dispatch
	overlays/public/home/.vim/bundle/fugitive
	overlays/public/home/.vim/bundle/git
	overlays/public/home/.vim/bundle/glsl
	overlays/public/home/.vim/bundle/pathogen
	overlays/public/home/opt/git-repo
	overlays/public/home/opt/taro