Add instructions to README for manually decrypting secure CSV

[kylenstone]

As a Next admin, if decrypt.html doesn't return an unencrypted file (due to some error), I want to run a terminal commend to try manually decrypting the file.

Add a sample command to the project's README so all project members can refer to it later.

Assumptions:

• Command should decrypt the entire file
• The simplest possible command with the fewest number of arguments will be the most useful.
• NEXT admin knows how to locate their local private/public keys and paste them into the command line, as well as how to access the destination file if decrypt succeeds.

[kylenstone]

I spent some time trying to write an openssl command that would utilize private and public .pem files to decrypt a copy of the spreadsheet.

I ran rotate_keys.sh so I could test on my local set-up: https://script.google.com/home/executions

I'm running this command:

openssl rsautl -decrypt -inkey rsa_2014_priv.pem -in demo_files/enc_test_1.csv -out demo_files/decrypt.csv

And hitting this error:

RSA operation error
4558:error:0406506C:rsa routines:RSA_EAY_PRIVATE_DECRYPT:data greater than mod len:/BuildRoot/Library/Caches/com.apple.xbs/Sources/OpenSSL098/OpenSSL098-59.60.2/src/crypto/rsa/rsa_eay.c:521:

Looks to be some kind of base64 encoding error. Hmmph.

[kylenstone]

When I try to use the decrypt tool Sky created, I'm getting a TypeError that looks to be deep in DataTables land. I think we should remove DataTables entirely as its not doing any work for us.