Details:  access PluginManager::instance() instead

Details: Moving files so that the local layout corresponds to the layout pushed by make install.
Adjust Make target, modify the resource path of the loader to find the resources in the
right place. All pathes are still looked up relative to binaryPath(), libs are found via
relative rpath.

replace ExtensionSystem::PluginManager::instance()->getObject<Core::ICore>() by Core::ICore::instance()

Task:     235982

Details:  - Conform to conventions.

Details:  - To make it conform to naming convention.

Details:  - And do some simplification/consistency.