Basic support for package categorization should be provided.
~/.sourceinstall/packages/ , current packages directory,
should contain one directory for each category.

Functions that handle package names should consider
package_category/package_name as a valid package name.

This becomes necessary as package number grows.
This also helps very much to identify the purpose of the
package (for example, a big X category can contain all the small packages which together form the X.org server - same with gnome)