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 support source files whose name start with `.` or
contain characters not allowed in the nix store, such as spaces.
Also add some test cases for `home.file`.
Added utilities to generate export statements and definitions for zsh scripts.
Currently, there is only lib.shell which generates export statements in bash
syntax. However, this does not allow to generate export statements for zsh
arrays (syntax: NAME=(elem1 elem2 ...) ), which would be the natural
representation of lists in the nix language.
