Set test variables in TestDesignerBeforeSuiteSupport/TestRunnerBeforeSuiteSupport

As a citrus test developer, I want to be able to set variables for the tests in the `TestDesignerBeforeSuiteSupport` hook to prepare my test environment efficiently.

As #392 shows, it's currently required to use a `TestDesignerBeforeTestSupport` implementation to manipulate the variables available within a single test. This implies, in the context of #392, that the same database request is performed before every test case. This can be optimized, if it's possible to manipulate test variables in the `TestDesignerBeforeSuiteSupport` implementations.