Simplifies setting `$zsh_dirs`

Previously, it would find:
- home directory
- owner home directory
- real base directory of `.zshenv`
- + any of the above prepended to:
    - .zsh
    - .zsh.local

Now, it only uses:
- real base directory of `.zshenv`
- apparent base directory of `.zshenv` prepended to:
    - .zsh
    - .zsh.local

Fixes two issues:
- removes home dir as a candidate
- fixes order (real base dir comes before .zsh.local)
Prevents error when Verman isn't installed

Still not ready for prime-time, maybe.
Adds `rust` Verman initialization