Removed cruft.
Updated documentation and readability.

 	modified:   ProfileInstaller.php
 	modified:   profile_installer.inc
Added documentation on how ProfileInstaller works.
Refactored ProfileInstaller. Move hook handling to InstallUtility.

	new file:   InstallUtility.php
	modified:   ProfileInstaller.php
Updated hook invocations.

 	modified:   InstallUtility.php
 	modified:   ProfileInstaller.php

  Simplify approach and remove duplicate code where possible. Add better
  documentation to explain the state of things.