Polishing
INT-2500: Polishing

* Change `IntegrationConfigurationClassPostProcessor` to check
if `CoreIntegrationConfiguration` is already registered with the AC and skip
'configuration processing'
* Provide ability to change global properties via `META-INF/spring.integration.properties`
* Rename framework default properties to `spring.integration.default.properties`
* Add test for combination of INT component scan and `<context:component-scan>`