PetaboxFileSystem refactoring:
- put reusable petabox related code in PetaboxClient
- moved ItemMetadata, ItemFile classes to petabox package.
- ItemMetadata test.
- src/test/resource directory for keeping test resources, updated POM
resolve the issue that block-compressed (concatenated) GZIP file
sometimes gets truncated at block boundary.
add buffering. enable by default.
CDXLoader: eliminated explicit reference to LFOnlyLineRecordReader.
PetaboxClient bugfix: was passing bufferSize to offset.