Removed unused imports
Updated UI opts and README

Made a more consistent UI with subcommands under the export command.
The export command is for exporting data and thus new types of exports
should be nested under the export top-level command
Changed name of IndexCommand class. Removed an unused Command
Updated list command

Now also prints the number of entries that an RdbType has
Changed hash in RdbIndexEntry from Array[Byte] to String

Also added readHash method in RdbFileReader
Made RdbIndexEntry in to a String instead of bytearray