Return status of network-level operations as an Enum value

As part of Spring Boot API that interacts with credbits framework, we need to return status of
network operation back to API. Below is a list of applicable statuses on each network operation.

1. **NetworkService.start()** - Should return a string (converted from enum value - Enum.Value.name())

Possible status values: STARTED (successfully up), RUNNING (network already running), ERROR_STARTING_UP (unable to start in case of error exit code from shell script)

2. **NetworkService.stop()** - Should return a string (converted from enum value -Enum.Value.name())

Possible status values: STOPPED (successfully stopped), ERROR_STOPPING (unable to stop in case of error exit code from shell script)

3. **NetworkService.terminate()** - Should return a string (converted from enum value - Enum.Value.name())

Possible status values: TERMINATED (successfully terminated), ERROR_TERMINATING (unable to terminate in case of error exit code from shell script)