Repository file format: group attributes of a package

* Introduce new package attribute B_HPKG_ATTRIBUTE_ID_PACKAGE (valid
  only in a repository file) to group the attributes belonging to a
  package.
* BRepositoryContentHandler:
  - No longer derive from BPackageContentHandler.
  - Add hooks HandlePackage() and HandlePackageDone() that bracket the
    attributes for a package. This is more explicit and robust than
    handlers having to guess when one package ended and the next began.
* BRepositoryCache: Make use of BPackageInfoContentHandler. No need to
  duplicate the code for reading a package info from package info
  attributes.

headers/os/package/hpkg/PackageAttributes.h

@@ -81,3 +81,4 @@ B_DEFINE_HPKG_ATTRIBUTE(52, STRING,	"package:post-install-script",
 	PACKAGE_POST_INSTALL_SCRIPT)
 B_DEFINE_HPKG_ATTRIBUTE(53, UINT,	"package:is-writable-directory",
 	PACKAGE_IS_WRITABLE_DIRECTORY)
+B_DEFINE_HPKG_ATTRIBUTE(54, STRING,	"package",				PACKAGE)

headers/os/package/hpkg/RepositoryContentHandler.h

@@ -8,7 +8,7 @@
 
 #include <SupportDefs.h>
 
-#include <package/hpkg/PackageContentHandler.h>
+#include <package/hpkg/HPKGDefs.h>
 
 
 namespace BPackageKit {
@@ -20,10 +20,24 @@ class BRepositoryInfo;
 namespace BHPKG {
 
 
-class BRepositoryContentHandler : public BPackageContentHandler {
+class BPackageInfoAttributeValue;
+
+
+class BRepositoryContentHandler {
 public:
+	virtual						~BRepositoryContentHandler();
+
 	virtual	status_t			HandleRepositoryInfo(
 									const BRepositoryInfo& info) = 0;
+
+	virtual	status_t			HandlePackage(const char* packageName) = 0;
+	virtual	status_t			HandlePackageAttribute(
+									const BPackageInfoAttributeValue& value)
+									= 0;
+	virtual	status_t			HandlePackageDone(const char* packageName) = 0;
+
+	virtual	void				HandleErrorOccurred() = 0;
+
 };