klighd: added startup hook extension point/interface for service loader.
This extension point allows any projects wanting to extend any KLighD
behavior for different run configurations to only need to register this
extension once via Eclipse extension and via Java ServiceLoader in
META-INF/services and programatically register everything needed in the
implementation of this extension with the KLighD API for registering
extensions programmatically.
lsp: removed KImage from reflective validation for the CheckImageAction.
As the potential circular links are not serialized in the
EObjectSerializer anyway, this exclusion should be safe.