Mock configs are now fields; EURUSDMockConfig is accessible via member
method.
Added unit tests for InstrumentPriceEngine.
Added method for second price query setup.
Added method for accessing USDJPY mock config.
Get rid of fixed prices for tick mocks. They are now configurable for
the history mock.
Removed unneccessary public price fields.
Minor refactoring: Static helper in generating an ITick mock added.
Minor changes in expectation helper methods.
Refactored UTs with contexts.
Initial implementation of PriceEngine class.
Grouped common tests in one method.
Added UTs for PriceEngine.
Added handling for instruments being null.
Added method parameter.
Added loggers to provide proper messaged when public method parameters
are null.