"EncryptionInformation.Method.IV" seems to have no use

[strantalis]

Today in the current implementations it seems like the EncryptionInformation.Method.IV goes unused which leaves me to think it is not needed in EncryptionInformation.Method. I propose that we remove this field as it is standard practice to generate a random IV for each encrypted chunk and prepend it to the beginning of the cipher text.

Also this will help reduce any confusion if someone is trying to implement the tdf3 spec in something other than cpp or javascript

[strantalis]

Another finding is that kas actually uses the iv in metadata block of encrypted metadata. So adding to the confusion of when IV is used.

#28