Implement file path resolver classes for making possible create own logic for test directory structures

[IvanChepurnyi]

• Implement interfaces and abstract classes
• Implement loader for current tests structure
• Implement loader for MageTest
• Implement loader for Magent 2.0 tests
• Create argument for PHPUnit running process that will controll wich test to include into the test suite.
  E.g. tests areas.

[IvanChepurnyi]

MageTest and Magento2.0 test are to follow in EcomDev_Test extension. But it is become possible to use fixtures separately from EcomDev_PHPUnit_Test_Case class.