General improvements

[Kestrer]

General improvements, including:

• Only prompting the user to run as root when necessary.
• Checking for sed
• Replacing incorrect usage of $_list_dir with $_log_dir
• Instead of removing all changed directories with a minimum depth of 2 when uninstalling, it now removes all changed files, and then removes their parent directories if they are empty. This means that there is basically no risk to uninstalling packages (unless a program you run depends on the existence of a directory even if it is empty).