feat(rest): provide example for rest http connector

This commit provides an usage example of camunda-connect
rest-http-connector, camunda-spin Json and camundaBPM engine

related to #CAM-2564
fix(bpm examples): proof read and correct ReadMes

related to #CAM-2587
doc(cockpit plugins): add plugin meta data for plugin store
docs(cockpit plugins): improve plugin meta data for plugin store
chore(cockpit plugins): remove accidentally committed MIT license
docs(cockpit plugins): improve plugin meta data for app store
Update README.md