changing the install location of hal-system-power-pmu to libexec

[Artem Kachitchkine]

> to /usr/share/hal/scripts, as it's quite clearly not a script.
> 
> In CVS, the hal-power-brightness-* scripts assume it's in the latter, so
> don't work for pmu at the moment. [1]

Why can't we just rename directory from an implementation attribute to something 
that answers the question "What's in this directory?" Because the answer 
"scripts" only sparks one's curiosity: "What kinda scripts? Can I put any script 
in it?" Calling it "method" or something is less ambiguous.

-Artem.