Implement update.check as a property

[stanculescu]

I changed the update check service to be set like a property (UPDATE_CHECK - default true) in gateway configuration, added unit and integration tests and deprecated the classes used for the service. I also added a new property SERVICE_URL that helps us to test easily the gateway behaviour. If the property is null(default value) it will be set to version.kaazing.com or version.kaazing.org

Issue https://github.com/kaazing/roadmap/issues/1076

[dpwspoon]

Additionally, I would highly recommend putting this in a new module. This may not be necessary but is for sure necessary if you are going to include a gateway.server jar in the surefire test, as done here:

+                <plugin>
 +                    <groupId>org.apache.maven.plugins</groupId>
 +                    <artifactId>maven-surefire-plugin</artifactId>
 +                    <configuration>
 +                        <additionalClasspathElements>
 +                            <additionalClasspathElement>${basedir}/src/test/resources/gateway.server-5.0.0.8.jar</additionalClasspathElement>
 +                        </additionalClasspathElements>
 +                        <argLine>${surefireArgLine}</argLine>
 +                        <skipTests>${skipTests}</skipTests>
 +                    </configuration>
 +                </plugin>

[stanculescu]

@DoruM Thanks for the review.