Complete initial version of library

[joachimmetz]

• add support for 0-byte filled virtual file
• add support to expose data in file from a specific offset e.g. to expose a single volume within partitioned image
• add support to fix corrupted/truncated live images of an NTFS volume
• add support to overlay recovered data on top of data in file, e.g. to implement Added a feature which can read restored Catalog data and Store data. libvshadow#18
• add write support, e.g. to replace EWF delta files replace delta segment file support by more generic solution libewf#36