This change makes use of the `extend` function inside `lib` to inject
a new `hm` field containing the Home Manager library functions. This
simplifies use of the Home Manager library in the modules and reduces
the risk of accidental infinite recursion.
PR #994
In particular, this entry notes that assigning lists to `home.file`,
`xdg.configFile`, and `xdg.dataFile` is deprecated and will be removed
in the next release.
- Default value is set to static '$HOME/.zsh_history' -- dotDir is not
prepended anymore
- $HOME is not prepended to the option value
- Ensure history path directory exists
Fixes#886, replaces #427.