OSGI support: add resources publish via HttpService

[arotnov]

In OSGI environment all static resources must be published by HttpService to be available through http. Vaadin has its own Service to publish Vaadin-dependent resources. And it publish its own resources like vaadinBootstrap.js by this Service. So, here is working code of Declarative Component for publish ChartJs resources by HttpService:

import org.osgi.service.component.annotations.Activate;
import org.osgi.service.component.annotations.Component;
import org.osgi.service.component.annotations.Reference;
import org.osgi.service.http.HttpService;
import org.osgi.service.http.NamespaceException;

import com.vaadin.osgi.resources.OsgiVaadinResources;
import com.vaadin.osgi.resources.VaadinResourceService;
import com.vaadin.osgi.resources.OsgiVaadinResources.ResourceBundleInactiveException;

@Component(immediate = true)
public class VaadinChartJsResourcesContribution {
	private static final String[] RESOURCES = { 
			"chartjs/Chart.min.js", 
			"chartjs/chartjs-connector.js",
			"chartjs/chartjs-plugin-annotation.min.js",
			"chartjs/chartjs-plugin-zoom.min.js", 
			"chartjs/hammer.min.js" };
    private HttpService httpService;

    @Activate
    void startup() throws NamespaceException, ResourceBundleInactiveException {
        VaadinResourceService service = OsgiVaadinResources.getService();
        for (String resourceName : RESOURCES) {
            service.publishResource(resourceName, httpService);
        }
    }

    @Reference
    void setHttpService(HttpService service) {
        httpService = service;
    }

    void unsetHttpService(HttpService service) {
        httpService = null;
    }
}

Declarative Service Component annotations could be used from org.osgi:osgi.cmpn:6.0.0. To create definition of DS component (@component annotation not processed in runtime) maven-bundle-plugin could be used.