Feature/reoranize and standardize terminology

[satello]

• Reorganize contracts. Contract implementations are now in contracts/impementations and abstract contracts are in contracts/abstractions.
• All implementation contracts are now stateful. This means that you have to load and switch the contract for the entire class. You should never pass the contractAddress as a parameter.

Note: Refactor of resource wrappers will be in following PR

[coveralls]

Pull Request Test Coverage Report for Build 585

• 67 of 99 (67.68%) changed or added relevant lines in 15 files are covered.
• 2 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+0.1%) to 45.262%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/contracts/implementations/RNG/BlockHashRNG.js	2	3	66.67%
src/contracts/implementations/PNK/index.js	0	1	0.0%
src/contracts/implementations/PNK/PinakionPOC.js	3	4	75.0%
src/contracts/ContractImplementation.js	46	48	95.83%
src/contracts/abstractions/Arbitrator.js	2	4	50.0%
src/contracts/index.js	0	2	0.0%
src/contracts/abstractions/index.js	0	2	0.0%
src/resourceWrappers/ResourceWrapper.js	0	2	0.0%
src/contracts/implementations/arbitrable/ArbitrableTransaction.js	6	9	66.67%
src/contracts/implementations/index.js	0	4	0.0%

Files with Coverage Reduction	New Missed Lines	%
src/kleros.js	1	0.0%
src/utils/isRequired.js	1	50.0%

Totals
Change from base Build 580:	0.1%
Covered Lines:	456
Relevant Lines:	841

---

💛 - Coveralls