Revert "Keep hash as String instead"

This reverts commit fc4ba091890b087eaa2501243a05c36a8f0779f8.

Revert "Made RdbIndexEntry in to a String instead of bytearray"

This reverts commit 0e21da5a4e3e1d46422468c0c52b9c274af75967.

Revert "Changed hash in RdbIndexEntry from Array[Byte] to String"

This reverts commit 1b45db51bbe482a831f6eb7526ea8bd8f5c04249.
Changed RdbIndexHeader to a case class
Change RdbIndexEntry to a case class.

To solve content equality between two RdbIndexEntry, the datatype of hash was changed to Seq[Byte]. Since it would refer to a WrappedArray through implicit conversion if an Array was passed.
Refactor. Made the test data fixture for the index file more readable