package kit: some fixes for multi-version support

* Use enums/constants/functions instead of preprocessor macros.
* Missing include in PackageInfoAttributeValue.h.
* PackageReaderImpl::Init(): Check version before header size and
  return B_MISMATCHED_VALUES instead of B_BAD_DATA, if the version
  doesn't match. This allows callers to determine the condition and
  try a reader for a different version. A more flexible interface for
  that case would be nice, but since we want to support the old package
  version only temporarily, the current solution should be good enough.
Clone read support functionality for HPKG format version 1

It uses sub-namespace BPackage::BHPKG::V1. Unlike the one for the
current format version, the V1 version of BPackageInfoContentHandler
lives in BHPKG(::V1) sub-namespace and is private.
Bump HPKG format version
packagefs: PackageLeafNode: remove superfluous declaration
BPackageInfo: Support reading both HPKG format versions
BPackageDataReader: Remove unused Size(), BlockSize()
package kit: Add BAbstractBufferedDataReader

It doesn't do much in terms of buffering, but defines an interface
buffered readers can implement, namely the additional
ReadDataToOutput() which currently BPackageDataReader specifies.
package kit: internalize BPackageDataReader

It is no longer public (or even private) API. BPackageDataReaderFactory
returns a BAbstractBufferedDataReader instead. The advantage is that
the latter doesn't have hpkg format specific dependencies.
packagefs: Add support for hpkg format V1

* Add union-like class PackageData which wraps the V1 and V2
  BPackageData classes.
* GlobalFactory: Create a data reader depending on the data format
  version.
* Package: Add a loader for V1 format and try that, if the other one
  fails.