Warn user about duplicate processor names

[luzhanov]

PROBLEM:

When you're trying to extract a config from the process group where some processors have duplicate names, the export goes without any problem. But later, during the config update phase, these duplicates lead to configuration conflicts which are hard to debug.

SOLUTION PROPOSAL:

1. Write a warning message to the log if during the export duplicate processors names were detected.
2. Add a command-line flag "failOnDuplicateNames" which will lead to the exception throwing if duplicate processors names were detected.