Feat/add store auth

[satello]

• Add Auth as a resource. It is included in the base kleros api as kleros.auth.
• Pass Auth token in header when we make POST or PUT requests.
• Add methods to sign auth tokens and validate auth tokens
• Restructure StoreProvider methods that pulled from shared store data that has been removed.
• Restructure event listeners that interact with the Store.

[coveralls]

Pull Request Test Coverage Report for Build 660

• 24 of 87 (27.59%) changed or added relevant lines in 10 files are covered.
• 5 unchanged lines in 3 files lost coverage.
• Overall coverage decreased (-0.1%) to 43.272%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/constants/error.js	2	3	66.67%
src/kleros.js	2	3	66.67%
src/contracts/abstractions/Arbitrable.js	0	3	0.0%
src/resources/Notifications.js	0	3	0.0%
src/utils/Web3Wrapper.js	0	4	0.0%
src/resources/Auth.js	8	15	53.33%
src/utils/StoreProviderWrapper.js	1	23	4.35%
src/resources/Disputes.js	7	29	24.14%

Files with Coverage Reduction	New Missed Lines	%
src/resources/Notifications.js	1	27.4%
src/resources/Disputes.js	2	38.86%
src/utils/StoreProviderWrapper.js	2	1.96%

Totals
Change from base Build 658:	-0.1%
Covered Lines:	434
Relevant Lines:	868

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💛 - Coveralls