PX+1) Add functionality to create offline integration tests

[gastonortiz]

In order to be able to always run the integration tests, making sure that we have performance in the tests every time we run them locally, offline integration testing needs to be done in the java client. To achieve this, responses for HTTP requests need to be mocked and returned when the tests are executed.
Offline testing needs to be disabled by parameter when invoking maven integration-tests so that by default they should be offline and if wanted to connect to the server, they should be online.
When running deployment and continuous integration, tests should be online by default.

[gastonortiz]

This ticket requires #6 to be completed before starting development.