NUnrar 0.8

Lots of little fixes and some API changes:

• Adding extras to API (IsMultipartVolume, IsSolidArchive, IsFirstVolume)
• Made RarArchive.Entries and Volumes be lazy so work is only done when needed.
• Added Mono target
• Implemented RarOptions.GiveDirectoryEntries
• CRC values for multi-volume archives should be correct
• exceptions are thrown for Solid and Encrypted archives since NUnrar can't extract them.
• Added IRarExtractionListener interface for getting the progress of extraction. Archtecture doesn't allow for real C# events.

Followed a lot of desires/fixes from users.  I like users of my code.