add support for PackageFilter in PackagesApi

[tubbynl]

draft on adding support for filtering Packages in the Packages api
fixes #755

please feedback on how te test this and/or the way of method overloading :)

[tubbynl]

build is green; but the added integration test fails

• it does work locally if i replace the setup in TestPackageApi

    @BeforeClass
    public static void setup() {
        //gitLabApi = baseTestSetup();
        gitLabApi = new GitLabApi("https://gitlab.com", "PERSONAL_ACCESS_TOKEN");
        //testProject = getTestProject();
        testProject = new Project().withId(PROJECT_ID);
    }

not really a works-on-my-machine; (also gitlab.com ;) ), but i think the test project does not have packages enabled?

[tubbynl]

Could you please do a review of this one @jabby ?

[jabby]

@tubbynl I will take care of the failed tests.