Changed en/decryption cipher to aes-256-cbc to work with Electron 4+.

[tonyanziano]

Fixes #microsoft/BotFramework-Emulator#1431 (comment)

Description

The Emulator recently upgraded from Electron 2.0.12 to Electron 4.1.1. Electron 4 ships with only one SSL library (BoringSSL) instead of the two (BoringSSL & OpenSSL) in previous versions. (Source #1)

This means that many of the recognized hashing functions used in the crypto library have been cut, one of which is the aes256 function which is used by botframework-config. This breaks any encryption & decryption in the emulator, so encrypted bots can no longer be used.

However, aes256 was just an alias for aes-256-cbc. (Source #2) (Source #3) This means that we can just change the cipher name to aes-256-cbc and we will achieve backwards compatibility while no longer breaking the Emulator.

Specific Changes

• changed the cipher name used in en/decryption from aes256 to aes-256-cbc

Testing

[coveralls]

Pull Request Test Coverage Report for Build #2202

• 2 of 2 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.05%) to 88.287%

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Totals
Change from base Build #2200:	0.05%
Covered Lines:	3237
Relevant Lines:	3524

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💛 - Coveralls

[cleemullins]

This looks good to me, but I would like @jspruance to signoff.

[cleemullins]

... I assume this same change needs to be made to the V3 JS SDK?