In the process of making UPower.conf customizable (#73968), it came up
that UPower doesn't load its config from /etc by default.
The UPower derivation is modified to make it load its config from /etc
at runtime, but still install the default config to its nix store path
as before.
The UPower module is modified to put the config in /etc.
- add missing types in module definitions
- add missing 'defaultText' in module definitions
- wrap example with 'literalExample' where necessary in module definitions
Using pkgs.lib on the spine of module evaluation is problematic
because the pkgs argument depends on the result of module
evaluation. To prevent an infinite recursion, pkgs and some of the
modules are evaluated twice, which is inefficient. Using ‘with lib’
prevents this problem.
