Ignore plugin config from signature computation

[varunvarma]

Also, don't use the built-in hash function

I confirm that this contribution is made under the terms of the license found in the root directory of this repository's source tree and that I have the authority necessary to make this contribution on behalf of its copyright owner.

[coveralls]

Pull Request Test Coverage Report for Build 450

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 93.965%

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Totals
Change from base Build 449:	0.0%
Covered Lines:	5325
Relevant Lines:	5667

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💛 - Coveralls