Adds OSGi Manifest Headers using OSGi plugin

This (unsolicited :smile:) PR uses the default Gradle `osgi` plugin to add the Manifest headers in order to make the component OSGi-aware, using the same mechanism (The `Export-Service` header) that the Camel core components and the official Maven Archetype for Camel Components.

I'm currently using it this way in a Blueprint setting (LR 6.2/Aries) which makes for very convenient Route deployment.