Possible features: filtering and groups

[Anders F Björklund]

> PackageKit has some backend requirements that
> it could be useful for Smart to implement...
> Typically these would require one implementation
> per package type, but the interface is generic.
>
> The first is "filtering", which is for selecting
> things such as development packages and so on:
>
> http://www.packagekit.org/gtk-doc/introduction-ideas-filters.html

For discussion I added the following package fields:

class PackageInfo(object):
     def getLicense(self):
     def isGraphical(self):
     def isDevelopment(self):

This implements the "free", "gui" and "devel" filters.

https://bugs.launchpad.net/bugs/254150

--anders