Multiple scenes, multiple robots and more

- workaround as ragconnect can not handle receiving lists yet
- added merging algorithm
- added tests for merging algorithm
- added some doc-strings in aspects
- test only against name of logical objects (as they might be copies now)

- remove jcenter
- do not use "apply plugin"
- put versions use in multiple places in variables

- address some build warnings

- add dry-run option
- check for running services

- as scene gets replaced, the connection is gone after the first replacement

- add "rewind" topic to restart app
- update ragconnect to allow mqtt handler with ports added to hostname

- lesson learned: do never throw an exception during attribute computation

- temporarily use unpublished, somehow fixed version of ragconnect