chore(engine): accept empty extending query for filters

related to #CAM-2630
fix(engine): use a copy for extending filter queries

- if no copy is used the cached filter entity persists the extended
  query

related to #CAM-2630
refactor: make DeployProcessArchive*Step extensible
Merge pull request #98 from rbraeunlich/deploySteps

refactor(engine): make DeployProcessArchive*Step extensible
chore(engine): remove package-info.java by package.html

- the package-info.java file was responsible that maven always
  detects changes and recompiles all sources even if no changes exists