Made ResultSet return -1 when no data exists.
Fixed an issue with recursion in parsing.
Refactored SeekableLittleEndianAccessor.

The thread-safe version is now a separate one.
Small logistic changes in preparation of laziness.

These changes have little-to-no performance impact on the eager-loaded
NXFiles.
Abstracted NXTables to add laziness support.
Cleaned up and improved javadocs.
Moved classes intended for primarily internal use.

Moved from main pkgnx package to internal subpackage to mark their
primary intended use.
Updated interface for NodeParser.
Implemented lazy-loaded NXFiles.