handling:
* package attributes are now compatible with the low level attribute
handling of other HPKG attributes (such that 'package dump' now shows
package attributes, too)
* dropped type names from hpkg format, the attributes were identified
by IDs already and this simplifies the code considerably. Type names
are now handled in BLowLevelPackageHandler only.
* instead of rolling their own mechanism, high-level package attributes
handling is now implemented via a corresonding set of
AttributeHandler-subclasses
* adjusted package writer to only write package attributes that are
needed (empty ones are left out)
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@40466 a95241bf-73f2-0310-859d-f6bbb57e9c96
