442471 allow adding resources to eclipse-repository

- copy target/classes content to target/repository
- add maven-resources-plugin to eclipse-repository default
  lifecycle (which will copy/filter src/main/resources content
  to target/classes)
- do not use target/classes anymore for temporarily storing
  launcher binaries during product publishing
- note that it is not possible to override any p2 repository
  files like artifacts.jar etc. using resources. 
  Resource files are copied before the repository is mirrored to
  target/repository, so published repository metadata takes precedence
  in case of conflicting file names

Bug: 442471
Bug: 424691

Change-Id: Icf77d070e7eb38227574d86bec32f7088de9ec86
Signed-off-by: Jan Sievers <jan.sievers@sap.com>